the half life of proviron is 12 hours.
whatever your dose is, to keep good blood levels of it in your system you'd have to dose twice a day to keep it consistient enough

that being said i've dosed it both inside 12 hour limits and outside 12 hour limits, my free test levels were great even on 25mg once a day, obviously better outside of it. i don't know how far the limits of free test being beneficial go, but i was happy with the less lower-ish free test levels alongside reduced DHT function that let me keep more of my hair on my coconut


so all in all:
personally i do 25mg ED and get good levels with great hair still