If a mature cow isn't progressing fairly rapidly after her water breaks, we'll put her in the chute and see if there's a problem. I would guess 30 -45 minutes after her water breaks. Of course, that's in a perfect world.. assuming you having nothing better to do all day then to watch your cows calf!
With a first calf heifer we try to run them up at the house pasture so we can at least keep a better eye on them.. they love to walk in anticipation of calving, and it seems I've chased one for miles if they aren't in a small pasture. With heifers we give them more time.. they tend to get up and down a lot, sometimes without a lot of progress. If she's laying on her side and really in hard labor with no immediate results (no toes coming out) then we run her in the chute as well. I've had heifers go for a couple of hours before actually calving, and still have a viable calf. It's really a judgement call. The longer you do this, the more feel you'll get for if she's having a problem.