"You’ll also need to make sure these wallets are up to date in case there are major upgrades. "
If you don't do this and keep the wallet updated, can you end up losing your coins?
Generally speaking... you shouldn't lose bitcoins. If you have appropriate backups and can access the private keys, the coins are yours and you will be able to get access to them, even if you need to use other wallets or software to do so.
Think about paper wallets... they are simply a private key printed on a piece of paper... how can that be upgraded? And yet, they're considered to be one of the most secure forms of "long term" bitcoin storage (assuming they were generated correctly and stored safely).
"Major upgrades" may cause problems with using the network, like when High S Value transactions were no longer allowed, if you didn't upgrade you would find that you could not create/send transactions to the network. However, your coins were not lost. They were still contained within the private keys that your wallet controls.
The only real scenario I can think of where not upgrading could really lead to losing coins, is a security vulnerability is discovered that allows someone to hack your wallet and gain access to your private keys. If you don't update your system you are effectively leaving yourself open to attack.