I think doing a speed run should be something you get an achievement for (like it is now) but I also think it's quite stupid to make people do it everytime to get a full clear. I'm sure they could find another, funner way for us to get that 5th chest. I like taking my time and doing things without being stressed or whatever. Not to mention the best drops come from that 5th chest, so you really feel compelled to do it everytime.