I don't know what other people do but here is a situation that rather grew over time:
The network uses 100% static IP addresses except for WiFi devices (of which there are few and are strictly limited).
There is no DHCP server EXCEPT for the WiFi clients.
We recently introduced a domain environment and the DCs/AD provide DNS now.
Everything seems to be working as intended / normally.
Today I noticed that the DNS system has been retaining records for WiFi clients and their respective IP addresses on the list.
I'm rather amazed that no real problems have occurred.
I see records going back to November still there and addresses duplicated 3 times.
I don't imagine that this is an unlikely situation so there must be something we need in our DNS setup to fix this??