How does one go about creating a magic item with a usage of rounds per day like boots of speed? I haven't been able to locate any magic item creation rules which talks about this, but it makes me wonder if it's related to charges per day and caster level. I can get close to recreating boots of speed, but I am missing something, which makes me wonder if that missing something is what I am looking for.
So boots of speed
As a free action, the wearer of boots of speed can click her heels together, letting her act as though affected by a haste spell for up to 10 rounds each day. The haste effect’s duration need not be consecutive rounds.
Haste is a 3rd level spell and caster level 5. So for crafting it should be a use activation wondrous item for spell level * caster level * 2000 which gives us 3*5*2000=30,000. Now boots of speed cost 12,000, so I need to bring in charges per day.
- 1 charge 30,000/(5/1) = 6,000
- 2 charge 30,000/(5/2) = 12,000
- 3 charge 30,000/(5/3) = 18,000
- 4 charge 30,000/(5/4) = 24,000
- 5 charge 30,000/(5/5) = 30,000
OK, so two charges gives us 10 rounds of haste for the same price as the boots. I could also use a single charge at caster level 10 for the same result but with a better caster level check vs dispel.
So I have recreated the item by cost and number of rounds, but never found anything about making it use rounds instead of a full duration. Since I can see many spells benefiting from this kind of treatment, I feel like there should be rules about it or a cost, but cant find any.