Over time laws and regulations keep piling up and very rarely congress takes action to remove or repeal them. Many laws still exist on the books no longer relevant.
Automatic expiration of laws and regulations will ensure that future legislators take action to extend only those laws supported by their future constituents.
Expiration schedule could be in direct correlation of the amount of votes the bill has received. As an example: Simple majority - 10 years, super majority 20 years.
Regulation created by non elected agencies like ATF, FAA, FDA etc. will expire after 5 years and will require an act of congress to pass it in to law during that period. Without act of congress, no regulation could be extended by the enacting agency.