Old Pokemon fan here, advice on on keeping a sentimental card?

I was really into Pokemon when I was 12/13 and it turns out that Pokemon had some kind of recent boom and my old collection was worth a lot of money. I’ve made a fair bit of money selling off the less sentimental cards but this one just happens to be one of my most sentimental cards because I got it during the original promo run on a holiday with my dad. It’s also worth the most 😅😅

1. ⁠An experienced collector who works at/frequents my card store told me that if I want to keep this card long-term I should open the sealed packet as the plastic on the back will leave a rectangular indent on the card. He says that there is already certainly an indent on it as it has been sitting in my childhood binder for years. However, I cannot see any indent and I doubt anybody except grading companies will be able to see it. I do not intend to grade the card.

I’ve tried getting advice from IRLs and card store staff on what I should do and I’m terribly lost because everyone seems to be saying different things. I really need this subreddit’s help! Thank you very much in advance 🙂

If I am not sending my card for grading, is it okay to keep it in the packet for long-term storage? Someone else suggested that I keep it in this plastic collectible card display box thing. Will this prevent the indentation from getting worse?

Honestly, I feel a little heartsick at the thought of opening the plastic lol.

Overall, is this card worth opening to preserve for long-term storage?

2) for some context I’ve outgrown Pokemon and I’m really into fashion now lol. There’s this made-to-order dress that I really want and orders close on August the 18th, but it’s not like I need the money to pay rent or tuition or something like that. I already have an offer for RM2800 (662.33 USD) but I’m quite torn on selling the card.

Because of this, I would like to know if you think this item will appreciate in value if I keep it for a long time more. Is it worth forgoing my dress order for? 🥲 Is this whole Pokemon TCG boom (especially with the Eevee popularity) just a fad? Do promo cards like these often appreciate over the years?

Thanks everyone and I would appreciate any help I can get 🙂