Sounds normal to me. I have a 49G+ and was chagrined to find that a fresh set of alkalines drained down to the lowbat warning in a few weeks even if the calc just sat around. Indeed, the way the calc ate batteries inspired me to not even use it, since I cringed at the waste of plowing through disposable batteries.
I have mentioned already several times here that, to my great satisfaction, 1000mAh Duracell rechargeables give me very satisfactory service, especially when I combine them with a quick charger and regularly back up my memory to SD card. The 49G+ is well used now, and I like it so much I may actually invest in 50G eventually.
I understand that the battery consumption of the 50G is similar. I also understand that some users are very satisfied using NiMH rechargeables in the 50G. This could be the solution for your exam situations--a full charge certainly will give more than just a few hours of use, so if you go into a test with a freshly charged set in the calculator you should be fine. Edwin Cordoba's BatStatus application for 49G+ is very informative for me, but I am not sure it would display correct information in the 50G, which takes four cells vs. three.
I do believe the "beep on" setting would increase battery drain. I also believe that displaying the clock also increases battery drain.
I don't understand why it would be inconvenient to change batteries during a test. Are you not allowed to keep fresh batteries on hand? Does opening up the calculator during a test arouse the suspicion of the examiner? Also, do you use the calc with the beep setting on, and if so does this not disturb your colleagues?
Les