I really don't care either way.

First time that came to my mind about time limits is that they tip the game a bit more towards class stacking, but one second later I decided class stacking is just a symptom of a deeper problem.

I think that at the moment time limits don't have any effect on gameplay and there is also the technical side. Running an instance takes computational resources, having no time limits would mean that a party can go afk inside a dungeon and keep the instance alive forever.