My horse has an eye condition that requires him to wear a flymask 24/7/365. He does just fine at night as far as I can tell, he lived out on pasture for like 6mo but otherwise has lived in a stall and he's had his mask on all the time for 5 years. I don't notice any scrapes or anything on him from running into things and I havent seen him have any issues with it. I would make sure you horse can see well enough in it though or ask your vet if you are planning to leave him out in it 24/7. It can kind of depend on the situation and the horse.
Also, check on it daily to make sure its clean and he isnt having any issues :) good luck!
My guy is outside 27/7 with a flymask on 24/7. He does just fine, I've never heard of anyone taking a flymask off just for nighttime. Flies stick around after the sun goes down too. ;) Posted via Mobile Device
I always remove my horses masks at night. I just feel there isnt near the need for them at night and I like to give their face a break so it isnt constant wear which can leave marks etc. I also use that time to inspect their eyes and make sure there are no issues or problems arising under there ;)