Oh yes, I've seen this on other sites (instantchess.com, I believe). If both players consent, time is extended. I would certainly like to see this implemented in live chess 3, if possible.
Accept a deal for extra time during a game?

I really dont like contriving rules like that. Maybe in unrated games.....
But I can already see posts in this forum by people complaining that their opponent refused to extend time in drawn or lost positions, or that they 'accidentally' accpted such a request. Bad idea, IMO. And if it ever gets implemented, dont bother asking me if i want to extend, my answer will always be NO.
What about making a deal for extra time during a game. Sometimes its very frustrating when youre on a draw or worse when youre in favorite and theres no time left. Offcourse many opponents dont care about there opponents time and dont make deals like that, but i think there are players reconsidering the time deal. What i saw in a couple of games people making (including myself) quick useless moves so the opponent draws out on time. I know you accept the time limit when going in a game but its just a idea for maybe improvements of the site. Sorry for my bad english so dont blame me for that please.