What are the disadvantages and threats of storing your cryptos in exchanges?
Btw, does wallet like nano ledger accept any amount of cryptos without having transaction fees?
The first question was already answered here: OP asked for a long-term storage and exchanges are more likely to close/be hacked/whatever what may lead to losing the money, as exchanges store your private keys. The answer to the second question I would like to know as well.
This is the most common problem for new users. They protect their wallets badly, and the savings have quite a lot. You do not need a good hacker to steal all the mediums if the protection is what it is.