Really interesting conversation.
In a way I'm fortunate enough to have focussed my collecting down to a team (the mighty Blues) that plays in a sport with a relatively small global following (Australian Rules Football). There are more than enough reasonably priced cards - taking into account inflation and relative rarity (yeh, I'm nerdy enough to have run the numbers) - to keep me going for many years to come before I even get close to completing my goal.
There are two factors that will contribute to this longevity. One, it is a lofty goal in any case, so completion is really a pipe dream even if not one more set of cards was ever released. Two, I have a strict budget for this that I must stick to, otherwise my naturally addictive tendancies will cause me and my family financial ruination.
The budget is the reason I put a lot of effort into making sure I do not overpay for anything. And to me, that is part of the game. To search not for the unfindable card (I haven't been in this long enough for that to be an issue yet), but rather to search for the card I don't have that someone is willing to sell to me for the price I am willing to pay. For a numbers geek like me, trying to define what that price will be is half the fun.
And even still, I will buy a box of the latest Select Australia AFL release as and when they come up. And why? Well, I NEVER bought a box as a kid. We were limited to the single packs we could afford maybe once a week or fortnight when the pocket money trickled in. I treat the box purchase as something of a gamble and treat for this adult version of the collector. Yes, I go back and sell a lot of what I don't want to keep on the bay, but never for unreasonable prices and really only as a sort of substitute for actual trading. I rarely make all my money back, but occassionally there is the thrill of pulling something that gets back the price of the box. This is only secondary to the thrill of pulling something I can keep in my collection that would have otherwise been difficult to obtain/justify. Select Australia actually do a pretty good job of making sure there's something worthwhile in every box. By definition it is unlikely that the resale value of the lot will make up the box price, and my experience is that I end up holding on to a fair few cards I'd rather be rid of, but that's the gamble and the price of the occassional thrill. This is totally unrelated to how I search for and price cards for my collection otherwise.
Note; I have also put rules in place for this. Only one box per release, no more. Again... addictive tendancies.
Then again, maybe it's just that box prices downunder haven't really significantly changed, and nor have the number of releases, for close to twenty years (with one or two really high end special release exceptions). There were more different AFL sets of tobacco cards in 1933 than there are mainstream card sets in 2020. Clearly the smaller market and limited following is working to my advantage.