I been a subcriber sincearound 2007 ish. I was able to buy a lifetime subscription at that time and it has been fantastic since. I'm not sure if they are still available or not but if you keep asking to talk a supervisor at some point you might just be able to wrangle a lifetime subscription out of them. Can't hurt to try? I believe I paid around $450 for the lifetime membership.
I did the same for a RoadyXT that I use in a Boombox at home and it goes into the Combine and tractors. Best investment I ever made. I wonder how many people bought the lifetime for their cars/trucks not knowing that they would lose it when you trade/sell.