Does SSD Health Decrease When Not in Use?

I have a 512GB Samsung SSD that originally came with my laptop, and I've noticed that its health is now only at 35%. I recently formatted my laptop and moved Windows to a secondary SSD, leaving the 512GB SSD completely empty. My question is, does an SSD lose health simply from being used, or does it degrade in health even when not in use? Since I'm not using it and it's empty, can I repurpose it as an external SSD? Also, I transferred about 15TB of data from this SSD. Additionally, does converting my disk to a dynamic disk in Windows impact its health? Thanks for any insights!