As the saying goes dont keep your eggs in the same basket. So have you saved all of your btc in mutiple wallets\software?
It's good idea to split your Bitcoin holdings in multiple wallets, and this can be software wallets, hardware wallets or combination of both using something like multisig setup.
This adds extra complexity but it also increases security a lot, and this should be done if you are holding larger amount of bitcoins.
I would never hold any bitcoin on centralized exchanges, and I don't consider this to be ''wallet'' at all, they should only be used for trading.
Should i make it 50:50 even though bitcoin core is always online?
I won't talk exact percentage and this can be different for everyone, but I would keep majority of coins in cold storage.
This can be created using software wallet on offline computer, paper wallet or by using hardware wallet that is most simple option.
You can hold rest of your holdings that you plant to spend periodically of hot wallets, and for daily transactions mobile wallets are perfect.