Constantly knowing that there is always something that needs finishing.
Always having to search for something and always trying to find somewhere to put it all.
The trouble sourcing drive-train parts, such as cassettes (NOS XT 8-speed cassettes are nearly impossible to find) and especially 5 bolt chain-rings in an 94/58 BCD. With those wear and tear items, it'll get harder and harder to keep the bikes running.