Is my strategy effective for the long term, or am I missing out on significant gains?

I am single and I have some disposable income due to the fact that I am earning in USD while living in SE Asia. I have seen a lot of ups and downs in the market, the hype, the craze, etc. I am not going to lie, I became part of it for a few months but I have pulled back because it is against my investing strategy in general. As a result, I sold some of my slabs that I bought during FOMO once it hit some ROI and became really careful with how I put money moving forward.

I am a conservative investor, 90% still in traditional investments like stocks, ETFs, bonds, lands, golds, etc. Then 10% is in Pokémon.

To avoid wasting money, I only buy the following:

- Sealed PC ETBs

- PSA 10 of Black Star Promo with PC stamp

- PSA 10 of some top chases that I really like: Bubble Mew, Generational Zard and Lugia V showing some booty.

- PSA 10 of JP and CN exclusive cards that resonate with me.

I met up with fellow collectors and investors at a card show. They saw my slabs and it seems like a “small” collection for them so I told them that I mostly buy sealed and exclusive products. They told me I am losing gains by buying sealed above MSRP even if it is below market and that it is easier to just buy the top chases.

Are they right that I am missing gains? I can hold every cards, slabs and sealed products that I have for at least 10 years. I don’t need the money and I have a space for it. I am having second thoughts now with what I am doing 🥲