It depends how fast you need it to be... anyway, I would recommend a small bonus time, like 2+1,3+1 or 4+2. But from the 3+0 Playchess online games, I do not remember that anyone reported time problems lately. It could make a difference though if you run a local match with ponder=off, that is why I think a small increment is better. It should also ensure a certain minimum of quality for long endgames.