Well, I don't have that many recordings I made (just one...) but I've been a concert photographer for 8 years now and RAW files from a DSLR (not the JPG) are comparable huge to JPGs. I have an external drive with all my photos on and every now and then copy the raw files to DVD RAM, not DVDR. Still, I never lost any of my burned Verbatim DVDR, which I mostly burn at mid speed or highest speed, not slowest. It's slow enough to copy files to DVD RAM which are only available in 3/5x and the 3x are WAY cheaper. You can do the math how long it would take to backup more than 300GB photos burning at slowest speed. There's only one set of photos I do have three copies of: 1 on an internal drive, and one on each of my portable drives (of which one is just a small pocket drive to take on the road).
I don't have the money to buy more backup drives right now. Additionally, all drive slots in my desktop are used and all the drives are almost full (total of 6.5TB) but I have to say, in way more than 10 years, none of my drives ever died. And actually all I know of that still exist, they are still working. I'm honest - I'm lazy and maybe should spend more time, care and money onto backup solutions. But tho all of this is great memory (photos, recordings and such) - in the end it's all just 0s and 1s, bits and bytes. It's not the actual memory and to erase THIS it takes way more than a power fail or a dying pack of technology
I'm actually feeling quite uncomfortable with external drives to be honest. Cuz the life time of a harddrive is never how long they run but how often they get started and stopped. My desktop pc's ever since have been running 24/7 when I'm at home (so they in the end get starts and stops maybe 10 times a year). So none of my harddrives ever will reach the 10,000 starts and stops they are averagely designed for. An external drive always gets started and stopped way more often. So that actually might die a lot sooner.
Actually backups are quite complicated if you can't buy as many drives as you want. I'd love to have one or two NAS storages, but tho I know they do have great prices for what they offer, it's just out of question for my budget. So I currently stick with getting DVD RAM when they are on sale.
Call me naive but I would actually never do all the effort in doing 3 or 4 copies and store them somewhere else or even in a safe box somewhere. I don't think that me and my tiny little stuff I do might be of any interest for upcoming generations so that I would need to store them that good. Maybe even I don't care for these things in like 30 years....