DVD's and pretty much all optical media are terrible for backup. they degrade just siting on the shelf. and one scratch and 'poof' goes your data. I'm surprised as a medium that they have lasted this long.
[1]"Manufacturers claim that CD-R and DVD-R discs have a shelf life of 5 to 10 years before recording," note that is "before recording"
[1] http://www.clir.org/pubs/reports/pub121/sec4.html
Sure, but shelf life won't be a problem when you burn a new disc every day and you intend to keep at most a couple of months' worth of daily snapshots.
As terrible as optical discs are for long-term archiving, I'm sure their shelf life usually exceeds that of a carton of eggs. That should be enough to protect against ransomware and most other kinds of disasters that can strike a personal computer.
a) Creating multiple DVDs each time you back up (if your dataset is small enough and stable enough that DVDs are an option, doing two burns seems like an acceptable burden to me).
b) Storing parity files[0] on the DVDs to allow you to actually recover from bit rot and disk damage.
