I've thought about this while vaked too. If I'm using my deluxe duel screen wand there aren't any problems, but being exposed to the air for 12-24 hours dries it out a lot and takes most of the flavour out of the vapour.
When I'm using the regular whip I keep a spare jar on hand for stuff that hasn't been properly vaped, so it's ready to go for the next time. But it would definitely be nice to just let it cool, put a cap on it and leave it for next time rather than having to reload.
Would save an extra 20 seconds.
But only the laziest of stoners(like me) would really worry about something like that lol
You could probably cut the neck off of a balloon and put the round part over the end of the wand. Would do the trick, as long as you let it cool right down to room temperature first... rubber like that has a tendency to melt.
I haven't tried this yet, but it crossed my mind while vaked one day...
You could probably cut a piece of cork to size and use that too, it wouldn't matter about heat so much then, but jamming a cork in the end might crack the glass.