How much CO2 leak is normal?

I had to get a rebuild kit for my regulator this year.  It started not holding the pressure I set (set pressure to 12#.  It might move to 4 or 15 with no warning) and dumped a 20# tank in about 20 days.  My 20 #-ers normally last 6-7 months.  First time in 20ish years of kegging I’ve had that happen.

The regulator on my portable kegerator was working fine, luckily.

Paul