In the admin image help files (since ever) there is a section regarding deployment of a new service pack.
According to the help, all you need to do is create the new service pack admin image and replace the share name of the new one to be the same as the already deployed one.
I have tested it almost every release and it did not work as expected almost always.
Two weeks ago, I decided to give it a go and try to deploy 2016 sp5 to my clients.(Currently, the users have 2016 sp3)
created the new image and replaced between the old share and the new one.
next morning when my users came to the office and fired up their computers I was waiting to see many deployments ( a couple of hundreds) and eventually, I got around 25 deployments and since that day there's a new deployment (one or two) each other day.
Up to now, we got around 35 deployments.
the real question here, is what causes the service pack deployment trigger? is it a registry key? is it a counter of the times firing SolidWorks?
for all those that will pop the obvious question, Yes I know for a fact that more than 80% of my users are working with SolidWorks on a daily basis.