Cleaning and lubing will only last a firearm so far. Parts wear and break, especially springs. The long term reliability of the firearm is the ability to find or make spare parts when they fail. In the absence of a company setup for long term such as Walther and Beretta, you will need a competent gunsmith that can make spare parts.
For the major components, I agree. Having a parts stash, or a reliable source, will keep things running far into the future.
To me, springs are like wiper blades and brake pads. They’re consumables that are going to need replacement from use (or even sometimes from lack of use, too). I can go OEM or aftermarket with a company like Wolff, who makes springs for out of production guns as well as currently made stuff.
A lot of my stuff was bought used, so I can’t give a round count on many of my guns, but I can look for signs of abuse/abnormal amounts of wear. This helps to give me a rough idea of how long it may last. Even my used guns should far outlast me, especially since I’m not an envelope pusher when I’m reloading ammo for them.
I do get a surprise now and again, like a newly purchased 629 6.5” Classic .44 Mag that had the tip break off the hammer-mounted firing pin while shooting with friends, a lightly used S&W Model 48 .22 Mag that locked up and has been in Springfield Mass. since June, or my used Dan Wesson .22 LR that decided to break the hand while I was shooting it last month. Those guns, while all are repairable, simply had small parts that broke out of the blue with no signs of imminent failure.
All in all, I believe that just about all quality guns, when given a reasonable amount of care and not having the pedal mashed to the floor with every bullet fired, should last for generations. The flip side is the less sturdy the construction, the harder you run it and/or the worse you take care of it, the sooner it’ll be scrap.
Stay safe.