If I'm understanding what you're asking... for us, encounters were encounters even if initiative hadn't been rolled. So a buff that got applied to a rogue that lasted "an encounter" could be used for the scouting, the return, and then the travel back with or without subsequent combat. The "encounter" was whatever the encounter was... even without combat.
I find that much more manageable to deal with than having a duration of "4 minutes", and then having to guesstimate how long it takes for the rogue to sneak up, scout, sneak back, pass on the info to the group, then move back up again. Too fiddly. Just say the buff lasts "an encounter" and then the rogue do his thing without needing to keep track of the minutia.
Yep, that was the question. There seems to be flaws in that as well. Now invisiblity or silence while you're scoping out guards literally can last all day because that's the encounter? If you then have a DM determine how long you can actually sit there before an encounter power actually goes away without combat (as to not abuse the power all day), isn't that akin to the DM making up how many minutes you've been sitting there?
I can see some benefit for not having to track some powers, but i still see some areas where it is still an issue determining how much time to let them sit there. I personally don't mind the time requirements/tracking all that much, but it's good to hear opinions on it.