The shorter the time limit, the more effective stalling/running/camping is. That's not what the game is about, it's designed and centered around taking all the opponents stock. Even without intentional stalling, some matches wouldn't be allowed to finish with a short time limit. Someone who's been involved in ruleset crafting please correct me if I'm wrong, but I'm under the impression we wouldn't even have time limits if it weren't for the fact that we need to move the tourneys along so that they can be completed in the allotted time.
Before anyone compares this to other fighting games, remember that Smash is not two characters depleting each others' health in a relatively small box specifically designed to have a timer going. In smash a timer just lets people win without necessarily seeing the match through to the conclusion it ideally would be allowed to reach.
On a different topic, all these anti-MK rules that people are suggesting are further confirming how much he dominates the metagame. Whether you're pro-ban, or anti-ban but with a bunch of rules to limit MK, you're admitting that MK is a major problem. Making rules that will screw with the rest of the metagame just to keep MK down makes a mess, while banning him stops the problem at the source, removing all of MK's direct repression of the metagame (through being way overpowered/broken) as well as the indirect problems (like the side effects of a bunch of anti-MK rules). I feel like all our tournaments are being set on fire, and some people want flame retardant Wiis and for buckets of water to be part of the venue fee, when we could really just arrest the one guy with the flamethrower who's torching everything.