PrC's that give spellcaster levels

[Emongnome]

I apologize in advance if this has been brought up before, but I can't find any references to this, so here goes.

Let's take a PrC that grants a +1 level to existing spellcasting class at only a few of the levels (Acolyte of the Skin from the Complete Arcane that grants it for 5 out of 10 levels for instance). Let's say that a wizard takes the PrC all the way to level 10 while advancing to a 20th level character (Wiz 10, AotC 10). At this point, he casts spells as a 15th level wizard. For his 21st character level, he takes another wizard level. Does he then cast as a 16th level wizard, or did he permanently give up the opportunity to advance as normal in his spellcasting abilities?

I couldn't find anything from the rules, but I've been known to miss things from time to time. If there are no rules, any ideas on what should be the case? Thanks.

 

[Zandel]

Your right he casts as a 16th level because his wiz levels are less than 20. He doesn't gain any BAB or other normal effects however he gets the epic ones in there place.

 

[Jack Simth]

He's still using the non-epic progression; he hasn't reached epic levels in his classes yet, so is still using the non-epic tables (for everything except that which is specifically changed by character level in your set of epic rules, rather than class level).

So 5 wizard levels later, he's casting as a Wiz-20; 5 more wizard levels later, he's casting as a Wiz-25 (but still isn't using the Epic Wizard progression, other than for spells - not feats and the like); his next Wizard level, however, gets into Epic Wizard, and he can get the assorted benefits of being an Epic Wizard (familiar's spell-like abilities, epic bonus feats, and the like)

 

[Zandel]

Point. I was talking about BAB and saves. Forgot about that bit.

In short you will gain the spells per day of a 16th the wiz bonus feats or an 11th and the BAB and save bonus of an epic. Not sure on skills but if you have the books with you tou'll know.