3 of 4 edited tags; edited body

How does Persistent Spell work with spells that have a duration?

How does persistent spell work with spells that have a duration? The ones that I am most interested in are constricting coils and black tentacles.

[Persistent Spell][1]

Whenever a creature targeted by a persistent spell or within its area succeeds on its saving throw against the spell, it must make another saving throw against the effect. If a creature fails this second saving throw, it suffers the full effects of the spell, as if it had failed its first saving throw.

[Constricting coils][2]

Duration 1 round/level

[Black tentacles][3]

Duration 1 round/level

Now the coils spell would normally end once you made your save, but from my understanding of the metamagic, you would now be forced to save against the spell again. Would this keep happening until the spell ends each time you made the first save but not the second, or would the metamagic feat only allow the spell to continue once?

As for black T, it remains until the spell ends. How exactly does the metamagic feat work on this one? Does the grapple check count as the saving throw in this case? [1]: http://www.d20pfsrd.com/feats/metamagic-feats/persistent-spell-metamagic [2]: http://www.d20pfsrd.com/magic/all-spells/c/constricting-coils [3]: http://www.d20pfsrd.com/magic/all-spells/b/black-tentacles