It's normal to see the initial swing and then a 3 to 5 psi creep over a few seconds until it locks up, especially on a new seat. Any creep longer than about 5 seconds is something I'd worry about and fix before I send it home with the owner.
Once a seating groove is established in the HP seat, it's common to see it lock up immediately at the top of the swing. Usually, leaving the reg pressurized over night and/or cycling it multiple times will speed the break in process. If you want to spend big bucks you can get a machine that will cycle the reg very rapidly and with very little airflow and adibatic cooling. But unless you service a lot of regs, it's not worth it - and it's not really needed in 99% of the time.
