I've tried all times of the night with great success. Works especially well when you can drive, pull over, shut your vehicle off, bugle, drive a couple miles, rise and repeat.
yep, that's how i have done it, and it works well. i have also started in with an area in mind at 2:30 or 3AM, and bugle my way there... if i am at a loss for finding elk, i'll do what i need to so i have something to hunt. i will bugle once, if i get answered, that's it unless it's too far away to get a good bead on him, if that's the case, i'll try to get him to fire off again to get a better idea.
if he's close enough to have a good idea of his location, no reason to bugle again.... a little common sense makes bugling at night low impact, and a good way to figure out a starting point the next day.
i don't do a lot of it, i don't get enough sleep as it is in Sept, but i'll do it if i need to, and it 100% works.
it always sounds like a good idea pre season, but then when the time comes, after 10 long days of chasing elk (or 20) and you are a little beat up, staying up until midnight or getting up at 2 or 3am doesn't sound like as good of an idea when already dealing with sleep depravation and fatigue from the hunting leading up to that.
it's something i always keep in the back pocket, and hope the season goes good enough i don't need to take it out of my back pocket.
i may do it more if i was hunting an unfamiliar area