If it had been an SCSI-Streamer and all the files had been tared on it, I would say that there would be a bigger chance to get those data restored after some years.

On the other hand, 30 Years are lot of time in my opinion - 20 years ago we switched from 8 to 16 Bit architecture, approx. 15 years ago we switched to 32 Bit machines and nowadays 64 Bit are affordable to normal people.

I didn't want to try to restore some files from 20 year old C64-disks now - and 20 years in the future I probably will find those old DVDs to crappy to try to restore some of the data stored onto them.