Not relying on one source of storage is okay but it still depend on individuals, individuals in the sense that some might be creating more disaster than they think they are protecting their coin when they have it in too many storage, like I have a friend who is a very careless person and a forgetful person, managing one access to a storage has been hell for him because he keep forgetting his passwords both to his wallet and to his email most time.
Every time he wants to log in after a while, it is either he does password recovery to log in, so people like that will find it quite difficult to manage several storage, but there is still nothing bad actually in storing in a storage, it helps you to be more organized and to be able to keep an eye on your coins at once.
Every time he wants to log in after a while, it is either he does password recovery to log in, so people like that will find it quite difficult to manage several storage, but there is still nothing bad actually in storing in a storage, it helps you to be more organized and to be able to keep an eye on your coins at once.
In this case, the joke is on your friend. This does not have anything to do with the safer or more secure manner of storing coins, whether single storage or multiple storage. This is all about an individual's responsibility or his failure to store or keep his passwords, seeds, keys, pins, and whatever important information in a safe place where he could easily access them.
As for me, it is always better to store your coins in multiple storage rather than on a single one. This does not need much explanation. With a single storage, it only takes a single attack for you to lose your entire portfolio. It will not happen with multiple storage.
We frequently hear about some service finding some kind of exploit in their code or some human error, causing people to lose coins. 
)) or any other kind of wallet when you have your private key, that would be fine for risk management.
