I replaced the pressure regulator on my home a little over seven years
ago, and installed an expansion tank as well. All has been well since
then.

About three weeks ago, I noticed that I was getting a LOT more flow
from faucets than I should be. I put the pressure gauge on the line,
60PSI - just like I had set it when I installed the regulator.

Tonight, the flow from the faucet was even higher - so I put the
pressure gauge on again. 115PSI. Wow. I turned on the hot water to
see how low the pressure would go, expecting it to either drop
quickly, or stay even. It did drop, but only over about a full minute
of use. Then, it stayed right at 60PSI, like it should, even after
the water was shut off. Since the gauge has a "maximum reached"
indicator, I left it on, I'll check what the peak pressure was in the
morning.

Thanks to the expansion tank, I haven't seen pressure raise like that
from the water heater. And even if the expansion bladder had failed,
I would expect pressure to drop quickly when water was used. Does
this sound like my pressure regulator is starting to go out on me? If
so, I'd rather replace it proactively...