I would think that folks probably have different arrangements in terms of coins they consider hot, medium and cold, and surely the practices could change over the years.
maybe in the very beginning a person keeps everything on an exchange, but he starts to learn about various ways to hold coins.. so the more ways that he holds coins, then if some of them are hot or medium, then they might be more vulnerable.. like how much might you hold on your phone for transactions, or maybe you don't hold much, but if you know that you are going to buy some expensive item, then you might carry the bitcoin on your phone for just that transaction.
you might have funds that you keep for transacting to refill your hot wallet or maybe transacting with friends and family (not on the street), so those might be medium storage, even though you still might need to be careful about UTXO management in tersm fo if some folks might see the balances in the wallets that you are using.. or maybe you learn about lightning network wallets and other kinds of wallets, so then you would still consider if those are hot, medium or cold, and surely the cold would have the most security, even though you might need to check in on them from time to time (once or twice a year or maybe more, depending on your situation), to make sure that you still have access to them.. Guys will make varying choices, and sometimes not want to get into too many details about what they do, yet I do sometimes post on coin management topics, and thin that the main idea is that there are likely levels.. and surely if you are buying $10 per week, it might take close to a year before you might feel a need to move those accumulated coins to a private wallet.
Managing one's coins is indeed a personal thing and depends on the individuals, and they surely have different approaches to what they consider hot, medium and cold storage. I believe it's normal to get started with everything on an exchange IMO, I mean a lot of people have, and then as they proceed and advance further, they can actually learn other secure ways to store their coins. And the more ways one store coins, the more one needs to think about security, especially when they're using a hot or medium storage method.
And for transactions, some might prefer to leave a small amount on their phone or use a particular wallet for that purpose, others might also prefer to use a completely different wallet for transactions with family and friends. UTXO management is also worth considering, especially when your wish to prioritize anonymity.
The LN and a few other types of wallets provides one with more options and each of those wallets has their own various security considerations. If we wanna talk about the most secure storage method, them it's definitely the cold storage, but it's not a set it and forget it situation, you've still gotta be checking up on it from time to time to make sure you've still got access to you coin.
Everyone has their own unique situations and not everyone are comfortable with sharing all the details that concerns their management strategies and that's pretty much understandable. IMO, the most essential thing is to have a system in place that works perfectly well for you and to be mindful of the different levels of security. If one is purchasing smaller amounts of bitcoin regularly, like $10 per week, I feel it's okay to just leave the coins in an exchange initially, but in subsequent time, you might eventually wanna move them to a more private wallet to ensure you've got an added layer of security.