How long does it take once an IMS starts to go?

[Perfectlap]

The issues with Boxster values has less, much less, to do with IMS (the average buyer doesn't know IMS from IRS) and much more to do with the same issues that plague older Mercs and Bimmers. Costs of maintenance and repair do not scale down with age. And as much as a well to-do middle aged buyer (the typical driver) would like, the Boxsters never going to have more than two seats.

The average Porsche buyer has kids, the bloated Carreras of the water-cooled era, though just as mass-produced as Boxsters, have that rear seat so wifey won't give hubby a ton of grief about buying a car that sits in the garage most days. Roadsters will always be the hardest to sell new and used. Once you add in the large quantities made, it further aggravates supply/demmand. It's the right car for the right driver only problem is there are very few of those drivers.

And if air-cooled Carreras were more popular in their day and not cars that nearly bankrupted the brand, to the point of being sold in water-cooled production numbers, they'd be losing value as well. That's the irony of Porsche values, the cars that saved the company are now too plentiful. You can now buy a water-cooled Carrera for the same $10K that it might cost to rebuild an-air cooled engine.