I did the same. Plus also I'm using on my Android phone. Replaces Dropbox completely unless I want to share something with other people. But for that case I usually use Sharing feature from Synology NAS.
I also have Syncthing installed on my home server which gets backed up. So I have a copy of all my files backed up there, in the event a laptop goes missing or dies.
The only use case I haven't yet covered is an off-site backup of my Syncthing folder, which would be sensible. I just don't know who I can trust with it.
Syncthing is designed as a sync solution but not explicitly for backups. You need some extra setup on top of the defaults for building a reliable backup solution.
If not setup correctly, any "mistakes" from one of the devices will automatically be synced to other devices and cannot be retrieved back.
In the case of a lost/stolen device, make sure you remove the device as soon as possible. If not a bad actor now possessing the device can delete and sync that back to your "back-up" devices too.