I understand. I do not buy current kits to hold onto in the hopes that they will be collectible in the future. That's not a very good use of my funds. What I do is if I see a kit I know is collectible but is under priced, I will buy it for the sake of selling it on eBay to turn a profit.
For example, my wife likes to shop old antique shops, flea markets and the like. When we were traveling through Texas in the mid 90s we stopped at a shop that had 4-5 of the old Bandai 1/48 scale armor kits. I had built a few of them in the 1980s and loved them but they were long OOP by the time I discovered the line.
I bought them for $10 a piece, a more than reasonable price. At the time, eBay didn't exist and I bought two of them to build, but only got around to building one of them (a Sherman). I grabbed the others because I knew they were hard to find, the price was right, I might have built them someday and at the very least, they would have been good trading material at a local show or club meeting.
Then during the eBay heydays the price for these Bandai kits went through the roof. I kept the built Sherman, an unbuilt T-34/76 (because it was the first of the Bandai kits I had ever built) and sold the remaining 2 or 3 kits (they were German armor and not my main interest).
I ended up making around $150 on the kits; although the price of one kit accounted for the lion's share of that amount. Anyway, it was close to triple what the entire lot of the kits cost me.
Could I have built them, sure, but I knew there were guys out there that wanted them more than I did.
BTW Monogram's Heritage Series and Revell's History Maker's Series were just an 80s marketing ploy to sell old kits that were being repopped. Many of the same kits were still fairly available at hobby shops in original or previous boxings. They weren't really collectible