Candle question

blowing out the candle ends the spell

snuffing keeps it going, you can light it later

thats the conventional belief. whatever

~Thor

Its up to you. Theres a lot of superstitions around this sort of thing. As said above, one is that if you blow it out that it blows away the spell. Its also believed that its offense to blow out a flame to Fire Gods/Goddesses or fire spirits. I snuff them out, but that's just me. I don't see any difference if it doesn't matter to you.