Viking, don`t you know a chessclock? A chessclock has one part for every player and runs only if the player has to move.And if the player has moved he pushs a button and only the clock of his opponent runs. So it is clear that you can certainly use the opponents time! For instance in 10moves / 30 days both player has to reach the 10th move until the 30th day is over but every player has the 30 days = 60 days (without weekends).And if you move 3-4 moves a little bit faster you have more time for the rest of the ten moves.Btw this is the regular mode which is used by chessplayers all over the world.In our OTB-Games (this morning I have lost:( ) we play 40 moves / 2 hours and then 1 hour for the rest of the game.That means that the game can run four hours until the first timecontrol (40th move) and after six hours it is over at the latest (today it was earlier) .In fast games we play an half hour in blitzgames 5 minutes (every) for the complete game.

ok, makes sense

I second Caissus' suggestion as an alternative for a few reasons:
1. It is more like real chess.
2. Taking more time over a particular move forces you to be quicker later in the game.
3. Less likely to time out accidentally.
4. Tournaments will have known time limits per round. A 40 moves/30 days + finish in 10 days, for instance, would be guaranteed to complete the round in 80 days.

Just my 3c