If you want to hold coins for 4-5 years long, altcoins are very risky to keep. Because they can drop down easily even when you least expect it. Yes, if that so, you can try shifting your coins and convert into bitcoin. This time, you will feel more confident to hold even more than 5 years i think. Because bitcoin no matter how often or long the dump season will be, it will always find way to recover and the best part is it's bount to set for its new ATH after it recovers.
True that, but sometimes alts can really, really surprise you. I bought some BNB when it just came out (I think I got a few as an airdrop too), and that was a very pleasant surprise. Same with few tokens I've decided to keep since ICO hype. Of course majority just went to hell but the remaining ones covered the rest and brought nice profits.