There are a couple ways around this.
Change your agent inventory settings to run an inventory at login and/or when the IP changes. Set the console to connect via DNS and not ip address (the default is both and this is a per-console setting). Set your IP lease in DCHP to be longer, but this may not help if you have laptops that go home with users regularily.
By default agents should be configured in the local scheduler to run a miniscan on IP address change.
Are your agents not configured to run miniscans on IP address changes?
they are but that only takes care of what is active any amchine thta had that IP previosly but has not miniscanned or scanned still has that IP
I can see where this coul dbe an issue in certain situations and the thread has some good work arounds. Maybe an ER that when the DB goes through maint it manages the duplicate IP addresses (maybe remove the duplicates, etc...) We use RCR in these situations and it helps.