Gamer Burnout?

I suppose there comes a time when each of us has to step back and look at how many games we're really playing in a week.  That in itself can be startling, once the hours are added up (for me it averages between 17 and 20, which i easily justify because it's all via chat or message board, so i can walk away from the computer as-needed to tend to my children, do housework and make dinner, etc. and no one's the wiser...right?), but my biggest downfall seems to be how many different systems i'm playing in a given week--right now it's 6.  And i am not keeping the combat formulas and whatnot straight.  Argh!  I find myself wondering if everyone has this problem, or just those of us that are math-challenged...or if the number of different games i play during a 7-day period is unusual.