If it's got to the point where they need maintenance, I recommend a very close examination of them. I had a Schaller strap lock fail on me mid gig. Close inspection revealed some wear to the pin, only very slight but it was enough with the downward pressure of the bass, to cause it to release.
I know that they are well regarded and generally very reliable but like most things, they will eventually wear and need maintenance or replacement.
These days I don't use them and instead rely on the little Grolsh type rubber washers. Cost effective, reliable, long lasting and any wear is easily spotted.