Time sniping

Could someone offer a clarification of the timing system (over and above what's already in the FAQ)?

What happens if a player's 240 hours has run out, and he gets into byo-yomi, then keeps waiting until that time has almost runout before making a move (all the while his opponent responds promptly, and still has 240 minutes)? It seems to me such a game (especially in 19x19 Go) would take a couple of years to complete, as long as the low-time player keeps getting additional hours and moving just before it elapses.

Any ideas?

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