The time limit is to add a challenge. I don't know what fall rolling games you have been playing but challenge keeps the game interesting. You can go in completely blind knowing there is a time limit and complete it. No you may not always be able to pick your party members and yes there are some serious windows lickers out there but it can still be fun.
I think 90 mins for timers is overly generous. What could be done is like how they did Dynamis for FFXI. Get small time extensions after certain criteria has been met but make a challenge out of it. Then again people whined about FFXI being too hard and look what happened to it...