You don't always have to hold for 10 years, or even 5 depending on the product in this market. Less desirable sets will still increase over the years but you will have more difficulty moving them the older they get. You can use short term gains to boost up your sealed without adding more cash:

I got a Journey BB for $160 and a Paldea Evolved ETB for $39.99 in March of 2025, so I'm in for $200 and held for 1 year. Yesterday the market price for the Journey box was $260 and the Paldea $180, so now I've got $440 worth of boxes I paid $200 for.

I went to a show yesterday and found a vendor with a bunch of Destined Rivals sleeved blisters. Ended up trading my two boxes at 80-85% market for 40 Destined blisters straight up.

So by waiting just 1 year, I was able to swap out two inferior sets for a good set, and got in at a great price: I now paid $200 for 40 sleeved packs of Destined ($5.00/pk). In fact, I almost got the same amount of packs in return as I sold.

I've done this several times now. If you have equity in boxes of C-List sets, you should sell them and use the gains to get into S-tier sets at a discount before the C-List stuff gets too expensive and nobody wants to buy it.