One of the benefits of the Switch Online service is that you get access to cloud saves. This means that your game progress will be saved to the cloud so in the event you lose your console, or get it replaced, you’ll be able to pick up where you left off. Unfortunately these cloud saves will not be kept and will be deleted should you decide to end your subscription.
This is according to a FAQ on Nintendo’s website in which it reads, “Save data stored with Save Data Cloud cannot be kept outside of the duration of your Nintendo Switch Online membership. Nintendo Entertainment System – Nintendo Switch Online also uses the Save Data Cloud, so the same applies.”
It is unclear if there will be a grace period in which cloud saves are kept before being deleted, but that’s something to take note of if you plan on subscribing. Interestingly enough prior to this it was also reported and confirmed that not all games will support cloud saves, with Nintendo citing reasons like cheating as one of the reasons.