Is it just me, or is there really no way to address a Sim's bladder need while you are in the tombs, and yet they never seem to pee themselves. Am I right in thinking that the bladder motive just suddenly fills itself while you aren't looking, or am I going crazy?

I took this "magic" to mean that the Sim had found a corner and done his/her thing out of sight.

I dont have the expansion and can't say if it actually fills, but if it goes down and they don't pee themselves...I dunno. I know it takes AN ETERNITY for a sim to have an accident this time around, maybe you're just lucky.

I noticed this as well. It was till around the 2nd or 3rd day of my first sims adventure that I thought "hey wait, I've been taking care of all my sims needs except for bladder". I checked and it was barely half full. I watched it for a while and I couldn't tell it if it was even dropping. This particular sim spent most of his vacation inside a tomb

Another set of sims however did need to use the bathroom more often, and were not inside a tomb for most of the vacation

Seeing that there is no real way EA made it possible to take care of bladder while in a tomb, I guess thier best solution was to make it so it doesn't drop at all

I am sure Pescado will soon see to that.

Egypt does have one tomb where you can deal with bladder if need be. The Sphinx has a hidden room that has a toilet and tub. They should have made a portable toilet (which people on the BBS insisted there was one in the game) like the shower in a can.