To what extent is a computer that is registered for MSU's DHCP guaranteed to get the same IP address every time it connects in the same building?

I thought I was told several years ago that the IP would always be the same until the registration lapsed.  Now we are seeing cases where the IP address changes between one day and the next (e.g. from 35.10.156.m to 35.10.156.n).  Is this a case of the DHCP server running out of available addresses and being forced to reuse an address that it otherwise would have "reserved" for the last computer it had been assigned to?

--Chris
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Chris Wolf                    Computer Service Manager
Agricultural Economics        [log in to unmask]
Michigan State University     517 353-5017