Weekly? I thought you had to do it after each channel open or close.. Anyway, you can of course make a cron job to automatically send the static channel backup file to a NAS in a different location every time it changes, to keep the channel backups safe.
That will depend on your risk tolerance. Umbrel will backup locally but, if you want another copy of the backup in case something happens to your Pi or hard drive you should use an interval you're comfortable with based on the value you have in your channels. I typically download a backup weekly.
What I learned is that you do need to create a channel backup after every channel open, both outbound AND inbound. This is because even though you don't have funds on inbound channels initially, eventually you may when you start routing.
Most importantly, the channel backup file is not going to back up your channels as the name suggests. It only allows you to close your channels in case your node failed. This way you can get all the SATs on your side of channels back. So, it really should be called channel funds backup.
RaspiBlitz has a useful service you can turn on that will automatically create an updated and encrypted Static Channel Backup file (channel.backup) any time a channel is opened/closed and upload it to your Dropbox account. Or you can have it saved to a USB drive plugged into the RaspberryPi. Or both if you're paranoid like me.
