I've also noticed this with my own candles, including pre-hiatus ones. (though sometimes they "burn out" and are really just disappearing due to a bug and reappear after a day or two IRL; sometimes they are actually burned out though) In particular, I have dragon shrines whose candles I keep perpetually lit, and I used to also have some sets of candles on tables that I turn on when I'm using that room at a particular time. My pre-hiatus shrines, which were perpetually lit, stayed lit longer than a set of three candles that I randomly turned on for a conversation and were immediately fully burned out the next day (the shrines stayed lit for about a week longer; I've since replaced them).