It would be nice to have time controls where you have a certain amount of time per game, plus some time per move. For instance "5days + 36hours", meaning you start the game with 5 days on your clock, and get another 36 hours for each move you make. This would allow you to take a break from a game for a couple of days, without having to resort to really long time controls that could drag a game to last months.

Littlegolem uses "10days + 36hours/move" which I find really nice. It allows you enough time to explore a hairy situation on a board, without having the risk in playing a game that lasts for years (some people make it a sport to wait time their clock always runs out to make a move. For every move they make).