No, it's not. The difference is that every write operation has a certain chance of failing and every day there is a certain chance, your hard drive loses information.

With the sun, there is no chance at all that it will destroy the earth in a million or a billion years. Plus, the universe won't collapse. Someday it will just stop expanding and stay that way (at least that's what recent experiments suggest).

You can even ask the company producing the harddrive how probable it is that information is lost. They usually keep very accurate statistics about that kind of errors.

I have lost more than one harddrive that way. Usually it starts with recoverable errors, e.g. the harddrive needs more than one attempt to read a single block, but once that happens the probability of losing more blocks grows very quickly and it usually doesn't really matter how old the harddrive is when that happens, - although the higher the load on the harddrive has been, the more probable it is...

Wrong, there is this fuzzy state. In a problematic block on your harddrive the data you read may change everytime you read it. It's a little complicated to explain, without going into details on how data is stored on the harddrive and what is used to read it but you can compare it to an old record that was played too many times. The sound just isn't as clear and brilliant anymore and you have to pay really a lot of attention to understand the lyrics.