Curious... they don't reboot, not even monthly, for monthly patching? That usually gets at least one reboot every 30 days or so.
If you mean "sometimes these computers are shutdown for days/weeks/months", then it should resolve fine when it powers on again... as long as the object still belongs to your domain, and the CM Sitecode is still there, the CM Client should just re-register, heartbeat, and get policies again.
Alternatively, do some web searching for the multiple "Client Health" type of scripts, GPO startup scripts for CM Client Health, or other methods other people have used and customized over the years to "keep cm clients healthy". Basically... I don't think you need to reinvent anything. There are lots of scripted methods out there already for maintaining CM client health.