I've never been in past my waist, nor have I ever been on a trip on which any partner of mine went in past their waist. I have gone in up to my crotch or waist 4 times I think. Once I wasn't roped up and my pack kept me from going all the way in through the snowbridge. Both feet were swinging freely in open air. F'n scary.
Once I got pulled (by the dumbshit on the rope ahead of me) into a crevasse filled with water. Good thing it was a warm day.
The falling-through-the-snowbridge method of going into a crevasse is most likely to happen in early "winter" before the snowbridges are strong enough to hold bodyweight or in "spring" when they are melting out. The month in which "early winter" and "spring" conditions occur are different every year, different for different elevations, ranges, aspects of the mountain, etc.
By sheer number of incidents, I'd bet crevasse falls are highest in June/July/August just because thats when the most people are out in the mountains.