I personally prefer storing my long term investment in my personal hard wallet because I find it safer. Putting your eggs in one basket would be a lot risky since hacking is everywhere and that could possibly happen even in highly reputable top exchanges. Store funds in exchanges for a short-term period and trading purposes only and make sure to keep your long-term investment in a more secured wallet where hacking isn't possible.
Exchanges are recommendable mainly for trading and they serves their purpose perfectly. There are various or numerous wallets, I use Binance which happens to be one of the most safest exchange in the space and difficult for some scammers to invade one's account, the only way that could happen is through phishing of spammed mails. Exchanges are used for trading but some traders and investors also stored their long term coins with exchanges favorable to them. I rather have my long term investment in a separate wallet like Trust wallet which only me can assess it with my 12 coded phrases.
Not your keys, Not your coins. A simple phrase that I believe since the time I learned it. There are many recommendable and has a good reputation exchanges but it doesn't mean they are safe from outside risks such as hacking. Storing your coins on them for a very long time is just not advisable a dumb thing to do if you are an investors.
I hope no one here who is planning to become a long time investor plans to store their coins in an exchange for a long time because of the additional risk it gives you. Simply storing it on your non-custodial wallet could give you peace of mind about your investment security.