This is a fair criticism and I am not defending the practice. My understanding is that time-bombs like this are very regularly introduced into all sorts of bill

This is a fair criticism and I am not defending the practice. My understanding is that time-bombs like this are very regularly introduced into all sorts of bills, party-agnostic. It's how they can say things like "We saved $X over Y years!" where a lot of the time-bombs go off half-way through the 'Y-years" bit unless renewed. Please correct if I'm wrong about this. I only know what I read, which is hard to trust anymore.