I used to stick it out no matter what. Now I don't care. There's no time limit. If I do stop it's usually around the 1 hour mark.
If I take the time to put it in the queue, prioritize in the list for three months, allow it to come to the top, wait for it to get sent out, slot it in one of two possible weekly DVD-watching timeslots, battle to preserve that timeslot with all the various demands of my time - I admittedly have very little patience.
For instance just in the past 9 months or so: Get Smart
and Confessions of a Shopaholic
didn't make it past 15 minutes.
There are a few I just started fast forwarding through. Hancock
Probably my most unpopular premature eject-ulation was Happy Go Lucky
. A gave that about an hour....although I think I'll give that another try sometime.