I have had the same Internet Provider for 8 years, he only has 56k dialup. Next Thursday I am getting switched over to a new Internet Service Provider (ISP), which offers DSL. Now I don't know how these things work in the tech ends that much, but I guess my IP will be different etc. Would you tell adsense of the change, or is it nothing that would set off a flag with adsense login etc ?
edit: You shouldn't worry, or even think twice about this. Google never stated anything along the lines of different IP's logging into the account, you can check your adsense account in the office, library, or in internet cafe hense all different IP's, google has no concern about that.
I've changed ISPs since I've had an AdSense account several times - never notified Google - never had any issues arise.
Forget about it. You log into your account using a username and a password, not an IP address. Why waste someone's time at Google?