How long should the turbo actuator hold vacuum

Bench testing my newly cleaned turbo and I got the rod adjusted to begin movement at 3 in and hits the stop at 18 in.
I left the Mityvac attached to check for bleed down.
After an hour it had dropped to 16in.
Of course, I suppose my MV may have a slow leak
But should a properly sealed vac pump and good actuator hold vacuum indefinitely?

If it only dropped to 16" after an hour, you should be fine. A leaky actuator diaphragm will go to zero in a matter of seconds.

Like said by sailor, a few minutes is sufficient. We are dealing with inexpensive Mityvac's and Chinese auto parts, not space shuttle quality. Expect a leak down to a low value of " Hg over time.

Thanks.
Now I am just waiting for gaskets and hardware and reassembly.