I just got a Fritzbox 7412 with firtz os 06.87 (German router) attached to my DSL. I guess that this router sets the lifetime of the old one to 0 before it changes the prefix.(also the preferred lifetime)
Schnittstelle 4: Ethernet 6
Adresstyp DAD-Status Gültigkeit Bevorzugt Adresse
--------- ----------- ---------- ---------- ------------------------
Öffentlich Verworfen 1h54m29s 0s 2003:d1:9704:2700:2c48:43a5:51ff:d554
Temporär Verworfen 1h54m29s 0s 2003:d1:9704:2700:3906:12c9:3b86:6b22
Öffentlich Bevorzugt 1h59m48s 29m46s 2003:d1:9733:7900:2c48:43a5:51ff:d554
Temporär Bevorzugt 1h59m48s 29m46s 2003:d1:9733:7900:3906:12c9:3b86:6b22
Öffentlich Verworfen 1h59m45s 0s 2003:d1:9738:7900:2c48:43a5:51ff:d554
Temporär Verworfen 1h59m45s 0s 2003:d1:9738:7900:3906:12c9:3b86:6b22
Öffentlich Verworfen 1h59m48s 0s fd00::2c48:33a5:51ff:d554
Temporär Verworfen 1h59m48s 0s fd00::3906:52c9:3b86:6b22
Andere Bevorzugt infinite infinite fe80::2c48:53a5:51ff:d554%4
Those were 2 prefix changes. Due to the fact that Windows lifetime changes are more or less irrelevant, these have remained the same, although I would assume that they have also been set to 0.
there is also a setting when you want to have your 24-hour forced separation
