In my opinion, the 4 hour time limit always is cutting it close, How many times I've seen people get it to floor 98 and then getting warped out because the time was up. What I'd suggest is a small little monster on some of the upper floors that you can kill for say 10-20 minutes extra, maybe more, maybe less.
I'd make it like plant status, immobile and passive, but with high level magic to make getting it sorta challenging. I'm not sure if you could add optional monsters that you don't have to kill, since iTower is programmed that you gotta kill everything on every floor or you can't progress. but if there was a way to work something like that in...
How about killing faster?
JK, yeah, one time I was at 96, then we ran out of time /sob
Characters: Magnus Elwyn - Hunter Magnus Blackbeard - Rogue Magnus Crowley- Mage- Future Wizard High Septon- Acolyte- Future Priest Magnus Thorvaldsson- Merchant