Spare parts can make the difference between a "shooter" and a "wallhanger" - no matter what firearm bespoken. Do not follow me as a role model, for after 60 years of firearms interest, I have a myriad of parts but no clue as to exactly what some go to....!! label stuff and at least keep similar things together.
Other caveat is equally simplistic: If something breaks and you intend to keep it, buy two replacement parts - one to fix the part and a spare when the replacement part breaks. Jonathan Browning original mainspring broke after many years and it was out of production. Replacement mainspring snapped the first time it was cocked. Bought two more mainsprings. Same thing with the next one. Remaining mainspring held but by then the supplier had no more mainsprings. Sold Jonathan rapidly. Lesson learned.