Spell-like ability modification

[JaminiMephit]

okay, so, I'm having an existential doubt, it's mainly for the prupouses of narrative but I'm trying to keep this as 'on the rulebook' as possible


Earth Mephits can enlarge themselves as a spell-like ability by using a level 2 Enlarge person ( http://www.d20srd.org/srd/monsters/mephit.htm#earthMephit )

is there any valid means to lengthen this time? spending a feat? reducing the casting of 1/hour to 1/(longer time for a more fixed amount of time?)

ideally, I'd say a duration of 10 minutes is more close to what I'd try to achieve here, any feedback is appreciated

[Morph Bark]

You mean to reduce the cooldown of the ability, you mean? No idea. If you did mean reducing the casting time or duration as your wording says, then there's quicken spell-like ability (a feat) or simply dismissing the effect.

[WaylanderX]

Maybe something like 5 minutes, but only once per day.
Time-wise, it is almost the same as 2 rounds per hour. Be sure your DM agrees with the change though :P.
You can also give the mephit an Extend spell-like ability feat (Found here (http://www.d20pfsrd.com/feats/3rd-party-feats/frog-god-games/monster-feats---3pp---frog-god-games/extend-spell-like-ability)).
You need to boost the casterlevel of that spell-like ability though, which can maybe be achieved by the Practised Spellcaster feat (does apply to casting classes only, but its not a far stretch to let it count on spell-like abilities).
A boost in casterlevel can also be achieved by boosting the amount of hitdie the mephit has.

[JaminiMephit]

Morph Bark, it is more of extending the -duration- of the spell, not reducing cooldown or casting time, sorry if my wording is odd, english isn't my primary language

in a sense, I am the DM, as silly and impractical as this might seem, I do want the story/setting I'm writing/drawing to be as compliant with rules and 'canon' as possible.

and since this deals with the main character and I want to add a sense of balance and avoid Mary-Sue-isms, I want to have a readily available explanation as to why this particular mephit is diferent


that said, I also play as DM for two local games, so in the end, it's information that could be useful in the long run :B

thanks for the feedback, you two!