The reason this is a good idea is beacuse I don't want people uploading entire fims.
I can get well over 10 minutes worth of play out of a 100MB file, but I dont want full films uploading.
10 - 15 Minutes MAX is quite enough.
I want to use that 100MB allowance for quality of clip uploads, not full length clips.

10 Minutes is adeqate for play length.

Thought this was supposed to be a YouTube clone?
Not very cloned if it doesnt utilize the same feature for the same reasons.
YouTube has this in place for these very reasons. Why else would I want it.

I want to limit the running time of videos uploaded.

But, It's Ok. Not to worry. If you can't do it, it's fine.