Where do long term holders feel most comfortable storing their stash?

First off - Sorry if this is a sensitive topic or rides too close to others privacy, or has been asked 1,000 times. Delete if not allowed, please.

I know the mantra from most is “not your keys, not your coins” and I understand that… but isn’t spreading out your holdings throughout different wallets/exchanges the safest play?

I guess I’m just wondering how many serious long term holders are doing this rather than piling everything in one spot.. any feedback is appreciated