Maybe here is another way to look at it:
The cars are like a Country Club Membership.
So many fun things to do, and many friends associated.
Lots of activity fees, but great equity.
Always an event or a party to go to.
If you are not interested in playing anymore - why stay?
Sell a few, and keep the junior membership.
You can always get back in.
However, if you truly believe that the prices will continue to dramatically rise, then keep them as an investment.
If not then no reason to sell.
We are all going to get out at some point in time. I just hope when i do that the market is high.