Yes and no.
while i run lgb almost exclusively, and have about 100 locos,
i stock parts i ‘know’ will wear out. Given my hoard having a ‘few’ spares is a reasonable hedge. Skates, brushes smokers, couplers, screws springs, idlers, bulbs, handrails, tires (which deteriorate over time), steps, lenses , etc. its more for convenience, but, some parts are increasingly difficult to find. Especially cosmetic parts. Its mice when youre in the midst of repair to have spares, including pesky fly away screws, springs, etc.
i have a few bachman parts that I anticipated might break, ie pilots and steps, so far so good. Id be lucky if these were the issues, compared to , say, shay pistons, climax drive shafts, etc. frankly with bachmann stuff, i have an attitude its works until it doesnt, then im sol. No parts, no support. May or may not be able to find a fix.
while less so, marklin lgb has demonstrated that some parts are also unavailable, even on relatively new models. like my saxon ivk, ik, roof brake system parts, etc., So, one could have a $2k loco that needs a part. Certainly has cooled my willingness to buy certain models because of this.
but…..i am amazed how often something oddball needs replacement. You really cant predict it all.
so, you take your chance and create a stash.
i have a lot of stuff from circa 2000 i still havent needed. I now buy what i need when needed.
in your case, perhaps a couple of ‘universal’ motor blocks with wheels, couplers, smokers