If the Rats filibuster, they lose the opportunity to ever filibuster again.
It's a race against time now. Will another liberal Justice die or step down while Bush is still Prez or not. If one does, and we don't lose our numbers in the 2006 election, then we can use the nuclear option when we really need it, which will be to replace a true lib with a true conservative. If we lose our numbers in the Senate in the mid-term elections, then we have problems, and probably won't be able to use the nuclear option after that. The ideal situation would be if a lib Justice leaves before the mid-term elections, but that is undoubtedly asking too much. But one can hope.