Time limits allow for the best kind of content to be created.

You should not punish failure. You should award success.

With a time limit, every group can accomplish something. Good groups can accomplish more. As it should be.

Nyzul isle, Salvage anyone? Bad group can clear 5 floors. Great group can clear 15. Bad group can kill one NM or mega boss. Good group can kill everything.

Every group accomplishes something. Efficiency is awarded.