Which isn't that bad. If your company is keen on having you stick around they can do the TN1->H1B->Greencard juggle in under a year. Otherwise, just sticking with your TN really isn't that different from being on a Greencard. Yes, you have to renew it yearly and the immigration folks can be surly about it, but you pay your $50 fee and you get another year. I did it for 10+ years without issues.
