I have the original Tin Lizzie (1996) on the original wooden frame. I have had to replace 2 parts in 23 + years..one was the presser bar spring, and then a week ago I had to replace the wheels(not technically a machine part)..they're part of the carriage. I bought a Qbot robotics system for it 3 years ago. It does everything I could ever need it to do...I am very happy with it.
Every time I see a longarm at a quilt show or shop, I always test drive them..just to see! My assessment is that the LA's in my price range are lightweight plastic, and I don't see them lasting 20 years...the heavier, more sturdier built models are all above 25K...so I stick with my old faithful machine. The only drawback that I can see with my TL is that the newer machines have a much faster response when in stitch regulated mode..but I don't usually use it..I use manual stitch or the robotics.
If you want to buy used..remember to calculate in the shipping or moving costs..as well as, if the frame is shipped, they often don't include the bars because it costs more to ship them than to just go buy new ones...but it's an added expense. You can get some really good deals on a used machine.There are used machines all over ebay, and if you decide to buy there, ask the seller very detailed questions, this way when you get it, if they have misrepresented it, you can get your money back.
I am in Herkimer County..where are you? If you're close, you can pm me and see my set up if you like.