all rides are different, I have done 8 so far, most in the SE, I did ride ohio.
Seems the 50's I have entered had 2 vet checks, Sciotto had three. The LD's usually one. I would suspect anywhere from 12-16 miles in general. Just depends on how the loops pan out.
COmpetitive, you can look online at that race last year and see what the leaders ran. In general for an LD Id say you need to be able to hold a 7mph moving average, with your horse able to pulse down in 15 minutes. that will give you a little fudge factor. You can go a bit slower for a 50 if there are only 2 vet checks instead of 3. Your pulse down time at the end doesnt count as ride time in endurance as it does in LD.. For LD the clock stops when your horse pulses down. So you have to leave time for that.
Last couple years I was running TWH, and trying to improve, I didnt really change much with hot weather, just kept riding and kept an eye on horse vitals. I did try to get out early. But it is what it is. You ride a 50 your gonna be out on the trail for awhile. You need to train int he conditions you plan on riding in.
Hopefully will be bringing my new horse home soon and will be getting him out on the trails. Maybe have him ready for a nov ride. How far are you from james river state park ? be doing a few days of training there in oct. Also probably get to graves mt at least once.