Not really, they don't worry about it because they have nothing to lose. If it expires then a few americans will buy some more guns, and there will just be a few more to confiscate when the get what they really want, which is total and complete confiscation of all civilian firearms.* They will just keep bringing it up until it passes, and as long as the majority of voters in NY, MA etc. keep electing filth like Kennedy, Kerry, Schumer etc. then they will have the clout to keep hammering on the rest of us.
Further, we have to win every time. They just have to win once. Look at the '68 full auto freeze. You don't see any politicians (or the NRA either) saying anything about repealing that one do you?
* Feinswine quote, "Mr and Mrs America, If I had the votes I'd take them all."