A sorcerer or wizard can recharge an imbued staff
At level 5 the prestige class incantatrix (Player's Guide to Faerûn 61–3) gains the supernatural ability metamagic spell trigger that allows the incantatrix to expend charges from a spell-trigger magic item to cause the spell the item casts next to be cast as if it had been modified by one of the incantatrix's metamagic feats. The cost is +1 extra charge from the magic item per metamagic level increase of the feat—hence 6 extra charges are consumed from a magic item when the incantatrix applies the benefit of the feat Persistent Spell (Complete Arcane 81) to its spell. Unlike the feat Metamagic Spell Trigger (Complete Mage 45), the supernatural ability of the incantatrix does not say, "If the metamagic feat’s level adjustment would normally increase the slot of the chosen spell’s level above 9th, you can’t apply the metamagic effect to the spell."
A sorcerer or wizard that takes the alternative class feature imbued staff (Dragon #338 58–60) replaces her familiar with an increasingly magical quarterstaff. That imbued staff can be made magical as if it were a normal magic staff by paying a +20% premium. However, so far as I'm aware, there is no magic staff that contains the 9th-level Sor/Wiz spell time stop [trans] (Player's Handbook 294). This means that the incantatrix must create an original magic staff that does contain the time stop spell. Doing so is subject to DM oversight (see Variant: New Magic Items on Dungeon Master's Guide 214), but, in short, the core rules would have this be similar to researching original spells (198). Once research yields a staff of time stop—that, according to Creating Staffs (DMG 287), typically has a market price of 115,050 gp—the incantatrix and a caster that can cast the spell time stop (and maybe that possesses also the feat Craft Staff (PH 92)) can work together through the winter and a halfway through the spring to make the incantatrix's imbued staff into a staff of time stop. (Don't forget to increase its price by 20%! By the way, the assistant could instead be an allied creature that possesses the spell-like ability time stop (see this question), or—if she's unconcerned with the tremendous additional expense—the incantatrix could just create the staff of time stop from a pile of about 150 3,825-gp-each scrolls of time stop. Maybe she's already a participant in the wish economy?)
When the incantatrix that possesses the Craft Staff feat also possesses a caster level of 12, she meets the prerequisite for the feat Recharge Staff (Dragon #338 60–1). That feat's benefit allows her to expend 5 levels of spell slots to cause her imbued staff to gain 1 charge. For example, expending 1 1st-level slot and 1 4th-level slot causes her imbued staff to gain 1 charge. (The 50-charge maximum remains.)
Thus, the incantatrix can spend 1 charge from her imbued staff of time stop to cast the spell and 6 more charges to employ the supernatural ability metamagic spell trigger to cause that time stop spell to benefit from the metamagic feat Persistent Spell. Then, so she can do the same thing during her tomorrow without risk to her staff's charges, she can cause her staff to gain 7 charges by spending 35 spell levels of spell slots. (Thirty-five is a lot, but she has over 60.)
The only real difficulty is achieving this before level 15. Both the feats Craft Staff and Recharge Staff compete for the incantatrix's character level 12 slot. A transmuter 3/master specialist 2/incantatrix 5 that then takes her next two levels in transmuter could meet these goals, taking the feat Craft Staff as her wizard bonus feat at transmuter level 5 and also taking the feat Recharge Staff as her level-up feat at character level 12. (Or she can just artificially inflate her caster level—either constantly or right as she reaches feat-gaining character levels (e.g. increasing her caster level to 12 at character level 9)—to be able to take "early" the feats Craft Staff and Recharge Staff as caster level 12 is their only real prerequisite.)
There are several ways this process just stops.
The DM rules that time stop can't be modified by Persistent Spell. The Dungeons & Dragons, Third Edition FAQ (June 2003) includes this exchange:
Assuming you are high enough level to cast a persistent time stop spell, could you use the virtual 24 hours the spell lasts to rest and recover your spells?
You can’t make time stop persistent. (Its duration is effectively instantaneous for purposes of the Persistent Spell feat.) (61)
(I am unaware of this ruling's provenance. Also, FAQ issues.) So the DM may wish to follow this advice. However, the DM should keep in mind that this advice is for Third Edition, and while Third Edition material that hasn't been updated for 3.5 remains game legal for the 3.5 revision (see Why a Revision? (DMG 4)), the time stop spell is updated by the 3.5 revision's own Player's Handbook—that could've seen the duration of spell time stop changed to instantaneous, but it didn't. That is, that the FAQ's suggestion was ignored by those doing the 3.5 revision may give the DM pause before ruling this way.
- The DM disapproves of the staff of time stop. If the DM says that a new magic item this basic can't be created, it's likely that no new magic items can be created. (And, while it is a variant to allow new magic items at all, if the DM's campaign introduction didn't mention an outright ban on new magic items, I'd be irked.) However, I can imagine a house rule like New magic items can't employ 9th-level spells if the DM were trying to maintain an air of mystery around the ring of three wishes (DMG 233) (97.950 gp; 0 lbs.) or whatever.
- The PC can't get enough gp for the staff of time stop. It's no small investment to create a staff of time stop. Raw materials for the staff cost 57,375 gp plus 300 gp for the masterwork quarterstaff. (The DM may waive this last because the incantatrix already has one.) Yet a level 12 PC typically has 88,000 gp at her disposal, so the staff of time stop is only most of it. (And only a small loan puts the raw materials cost of a staff of time stop within reach of even a level 10 PC.)
- The PC can't access a time stop effect to create the staff of time stop. No one should be so incurious as to help another create a staff of time stop. It would take a peculiarly long and particularly strong con to get a dude or monster that can employ time stop once per day to employ that on the incantatrix's behalf while they spend the 8 hours a day for nearly 5 months making her imbued staff into a staff of time stop. That, however, may be the adventure.
Note: The Player's Handbook on Spellcasting and Services says that one can just pay 1,530 gp for a wizard 17 to cast time stop. However, according to the Dungeon Master's Guide on Community Modifiers and Highest-level Locals (139), default towns never contain a wizard higher than level 16. A metropolis may have a cleric who is as high as level 18, and several domains make available the spell time stop like the Player's Handbook domain trickery (189), but the Dungeon Master's Guide puts the chance of a randomly rolled town being a metropolis at only a 1% (137). Really, it's easier to find a Wiz17 during play (and in Faerûn!) than it is using the core rules.