Remember that lemmy instances are run by volunteers not companies so there may be some risk in a lemmy instance closing down and you losing your account.
Your posts will still exist as they have been federated to the other instances at large but one annoying thing would be losing all your subscribed communities.
When you have a nice account setup, you should stay safe by creating another account on another instance as a backup and following this post on how to have it subscribe to all your communities for you.
Alternatively you can subscribe manually but it can take a long time if you subscribe to a lot.
Either way having a backup account would be good practice. If this is your main account here that is fine and so long as you have another account elsewhere on another lemmy instance with the same communities subscribed in the event of a server going dark it wont affect you.
Here is the post with instructions for windows : https://discuss.tchncs.de/post/343976