Almost all OEM's have a PPOP (product phase out plan). It goes something like this (using
BX2350 as an example):
Direct parts support for a vehicle will be sustained for xx years. Typically 15 years is used. So, for instance, once there is a replacement for the
BX2350, all parts in the
BX2350 are available for 15 years.
Part substitutions - During the production life of the
BX2350, newer parts may be introduced on other tractors. These parts my be used as direct or kit substitutes for the
BX2350. If you order a seat, you may get a seat from a B2685. It bolts up directly, and is a substitute for the OE
BX2350 seat.
As time marches on, and 15 years have elapsed, it doesn't mean you can't buy any parts for the
BX2350. Many parts can be replaced with upgraded or replacement parts. Castings and specialized machining parts are the first parts to normally go obsolete.
Higher volume unit sales help in the extent that third party companies become interested in providing will-fit parts. Ford 8N's are a great example. I can't even start to count the will-fitters that are manufacturing parts for Ford.
Contrary to belief, OEM's are reducing their long term service parts support. You won't see as many companies supporting products for 30 years. The trend is to have a more defined support plan, and move people to newer machines.
IowaAndy