door lock duration spec?

[KenB]

I've been troubleshooting my vacuum locks, found the problem areas, and for the time being, just blocked off the lines to the leaking elements. The vacuum used to run out after about 10-15 minutes but now it's lasting much longer and it got me to thinking about how long it's *supposed* to last. Frankly, I'd be thrilled if sufficient vacuum was preserved for 1-2 days but I'll bet it's really supposed to last longer than that.

So, how long?

KenB
1980 300TD