Sha'ir and PrCs

[Zanos]

Do prestige classes that progress casting increase the amount of time a Sha'ir can keep a spell stored and/or their diplomacy bonus on retrieving spells? Both abilities are under the "Spells" entry for Sha'ir, so I wasn't sure.

I'm guessing the answer is no, but most advice for Sha'ir seems to be to prestige out asap because the class features are lackluster, but it seems like it would be rather awkward if all of your retrieved spells suddenly disappear several times throughout an adventuring day.

[Xuldarinar]

Personally, I do not believe that anything but levels in the Sha'ir class advances how long you can store a spell, nor diplomacy bonuses. While a part of the class feature, no special rule is made for advancement and most entries regarding advancement are specific in what they progress (Caster level, spells per day, spells known).

Purely RaW, its not advanced. RaI or what a DM should permit, are different stories.

[Psyren]

Actually it's a feature, not a bug. If the spell drains away you aren't stuck with it overnight.

Past level 6 (When you would be PrCing anyway) it doesn't even matter, since that's almost the whole adventuring day per the DMG.