According to Speedy Jim :
David wrote:

Problem: House pressure rises during the night from 40 PSI to 70 PSI.
Is incoming pressure regulator failing?

Yes. Even the tiniest of leakage past the regulator will slowly
increase downstream pressure. The valves are quite rugged and the
leakage could simply be due to dirt accumulation. But, hey, if you
have to remove the thing to clean it you might as well replace it.

Plan "B": Leave some faucet open to drip just enough to compensate.

Plan "C": ignore it. Unless you're worried about your plumbing rupturing
from 70PSI, it's not a problem. It'll instantly drop to 40PSI the moment
you start using it.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.