While I'm the absolute opposite of the preparation-junky, Maptool has also doubled my prep time, so I have empathy for you there.
It seems like you're enjoying it, and if your players are as well, couldn't possibly hurt...
Any time you organize and lead a group of people in an activity, you really ought to be considering their wants and needs. Being a jerk to them is likely to result in their rejecting your leadership as soon as they are able.
GMing is no different.
Sean Reynolds from Paizo has an idea for nix-ing XP that still gives out carrots - http://www.seankreynolds.com/rpgfiles/misc/AlternativeLevelAdvancement.pdf
Basically each level is cut into quarters (steps) and you get one per four hours of play.
Back in college I had an Earthdawn group that fluctuated between 8 and 12 players. I recruited one of them to co-GM the sessions, just as above, but we ran the game simultaneously. We deliberately split the party up as often as we could, and where we couldn't we'd at least split the combat...