But I don't care much for 'encounter' as a definition of duration. It's too vague and variable for my tastes. And I know plenty of players who will argue for 'encounter' meaning one thing when it's to their advantage and another thing when it isn't. Or they'll compare two encounters of different lengths and point to some perceived unfairness, between the amount of trouble they were able to cause in one encounter compared to how the same effect caused them so much more trouble in another.
I think the answer to this is easy - put the length of the effect in the players' hands, with consequences. When I run 4e "Encounter" duration means until the next Short Rest - which the players choose to take (or not). Either they keep their buffs but don't recover Encounter powers or get to use healing surges freely, or they get to use surges freely and recover Encounter powers but lose the buffs. Simples.
The only duration I find a problem in 4e is "lasts until the start/end of the turn of the one who imposed the status". I really wish that one would go away, as it's a PITA to track. I'm fine with:
- Instantaneous
- Start of the
affected creature's next turn
- End of the
affected creature's next turn
- Save ends
- Encounter (i.e. next Short Rest)
- Day (i.e. next Extended Rest)
"Sustain" is fine for effects that aren't statuses on another creature, and this is mostly what 4e uses them for, to be fair. Things like Stinking Cloud, Conjurations, Wall of Fire and so on are fine if they can be sustained by spending an action every turn to keep them up - and it's self-limiting, in the sense that a caster only has so many actions and so can only sustain so many effects.
Durations in "rounds" or "minutes" I always found combined the worst of all worlds. They need tracking (the idea of "announcing round number" seems weird, to me, since 'rounds' don't mean much once action of any sort starts, especially if delays and such like mix things up) and yet are still arbitrary outside combat, since the DM has to guesstimate how long all sorts of things take (and, as a former project manager, I know just how accurate
that tends to be!) Not to mention that in a pseudo-medieval setting, such measurements would be quite anachronistic, to say the least...