Strange having such a short lease period on cable.
I have had the same IP with Comcast for over six months and that is with many many modem reboots.
I was surprised when I had addresses on four separate Comcast networks within a four hour time span (Thanksgiving week, Nov 2011). Routing was very strange, too, at that time.
During that particular week, I also rediscovered the (not so surprising) fact that there is an inverse relationship between WAF and nagging...