I have Cat, Case, New Holland, Komatsu,and some minor brands of equipment; and I have Mack and IH trucks. I buy everything used.
I no longer buy IH trucks or New Holland equip. because, unless they are new,they are basicly unsupported by the dealers in this area.
I am a great fan of Case backhoes, but we didn't even have a Case dealer in this state for a year or so after Briggs pulled out. Our dealer now is a new startup company, and time will tell.
I bought both of my Komatsus this year, neither from a dealer, and the support seems very good, but I'll know for sure later on, I guess.
Caterpillar and Mack both support their machines very well in my experience, no matter the age. I do not run machinery under warranty, so I can't speak to that side of things. Both the dealers and the manufacturers seem to want to help anyway they can, for a price, of course.
My point is, the support you get seems to depend heavily on the individual dealership. My IH dealer has said things were unavailable that another dealer 300 miles away had no trouble with.