All laws should have sunset provisions. No really, I mean it.
Those with strong support should have longer terms, maybe 100 years, but even the "obvious" ones should have sunset provisions. The Constitution? The only reason it has survived so long is because it has been modified, which is the whole point of sunset provisions. Do you think the Constitution would still work today if the three-fifths clause were still in effect or if women couldn't vote? The point of sunset provisions isn't to get rid of laws, but to give people an opportunity to correct problems with them. Yes, we correct problems with laws, but it takes an act of congress (literally) to get a law modified that desperately needs it, and you can forget about improving the hundreds of laws that have lots of problems but aren't on anybody's campaign points.
Or would you argue that there should be sunset provisions on the laws against murder?
Yes, of course there should be! Yes, murder should be illegal, but no, of course the laws we had for murder in the 1800's should not be in effect and they absolutely should be re-evaluated after a reasonable period of time has passed.
1800: Senator Bob: So it looks like the murder law is in sunset, do we vote to renew it?
1800: Senator Kim: No, my constituents think hanging is barbaric and want to switch to the electric chair, so we need to rewrite the law.
1900: Senator Ralph: So it looks like the murder law is in sunset, do we vote to renew it?
1900: Senator Kelly: No, my constituents think murder shouldn't have an automatic death penalty, and some people should just be imprisoned, so we need to rewrite the law.
And the budget? While I'm making imaginary changes to how US law works, I have a fix for the budget problem too. It should be required to be set three years in advance, with Congress and the Senate sequestered, with no other legislative action allowed until they have passed it. Emergency funding for unexpected issues should be what gets debated, not what we could have seen coming three years ago (or 50 for that matter.)
Every new law should have a sunset provision of 1 year to give it a chance at debate every year until (at least) every representative who was present when it was introduced is out of office. After that set a cap of 10 years, then 20, then 40, then 80 and max it at 120 since that's long enough that you can depend on the generation that got it passed to have also passed.