You finally determined your domain name AND it's available! So you jump on it and buy it. A couple of months later your receive a notice in the mail that you need to renew or lose your domain name. What do you do? IGNOR IT.
When the legitimate time comes, just renew with who registered your domain with in the first place or shop around. You are allowed to transfer to any registrar of your choice.
NOTE: If you go with the big Daddy of them all, expect constant upsells. Again, you have options. Do your research and ask around.
Taking all of my experiences