The duration of prestidigitation is kind of all over the place. The main entry for duration is dual:
Additionally each effect may or may not add wording like
for 1 hour
until the end of your next turn
My question is regarding the effects that do not specify the duration in their description. For example:
You clean or soil an object no larger than 1 cubic foot.
If you clean the object it is instantaneously clean, but will it automatically and instantaneously re-soil itself after an hour?
You light or snuff out a small fire.
If you instantaneously light a small fire, will it automatically and instantaneously snuff out after an hour?
Since the duration isn't specified in the effect description I think the global duration "Instantaneous/1 hour" applies, but I've played with people who disagree and think that the effect is permanent.