For me it depended on which model......my 1st GTC - 9 yrs. by 1st BB- 15 yrs, QM - 2 yrs, 1st C/4 - 4 months, 2nd C/4 - 2 yrs, 2nd GTC - 7 and counting, Dino 3 yrs and counting......2nd BB - just got it.
The newer cars were less.......355 - 18 months, 360 - 6 months, 550 - 2 yrs, 575 - 2 yrs, SA almost 4 yrs and counting
I have found it's hard to predict what I will do. I think my GTC is a long term car......especially with all the work I have had done to make it a better GTC. BB being a Carobu special should be long term, Dino is on the bubble.
Current: SA, 330 GTC, Dino, BB, QP
Past: GTC, BB, QM, C/4, 355, 360, 550, 575, C/4