That is the thing about Nokia phones. You need to abuse them regularly, otherwise they wilt and die on you!
With SIM cards, the phone numbers and account are tied to the SIM card, so you can change phones with little issue.
I have no idea of how long the data service will last. It should last for a while, Rogers is making good money out of it. I suspect someone at Rogers figured out most people will pay only so much for data, if they charge more, the subscriber rate drops dramatically. Most any other carrier in the world can make money at this rate. Why would Canadian carriers be any different?