Unless I want to edit something, or it's for a job, I copy the files from the SD every few days, organized them, update the DNGs (the out of the drone DNGs don't apply inbuild DNG lossless compression, so they are bigger than they should, it can be done with Lightroom for example) and use Free File Sync to backup the files to an external 2.5" HDD.
In general, to avoid file loss you need to have the files in at least two different places, for example the SD and an HDD, or when you delete the files from the SD, on two HDDs.
If you are on a travel, bring two portable SSDs and copy the files on them, don't use 2.5" HDDs on the go because they are quite fragile and they won't survive a fall to the ground from just 1 meter height, while an SSD will surely survive.
Then, when you arrive home from the travel, you can copy those SSDs to HDDs, which are way more safe to store data long term.
Data redundancy of two is usually enough, but you can mess the files during the copy and accidentally delate them, both the original and the copy, that's why data redundancy of 3 is the optimal, but I personally use two, which is already twice the cost of living on the edge, like 99.99% of the folks out there.
If you don't care about price per GB, you can pick a NAS, but I personally prefer to pick external 5GB 2.5" HDDs because you get more GB for the money and you can store them elsewhere after being copied, much like the CD/DVDs backups some years ago.
PD: I also recompress the video files with Media Encoder (keep the resolution, but lower the bitrate), because I just take them for curiosity/exploration purpose, so they are not as valuable as the pics to me.