Greetings: Just from my own experience, some DVD media is more reliable than others, and the recording device can contribute to the life of the DVD as well. One size does not fit all so to speak. I generally record at the slowest speed possible to get a consistent, constant burn as possible. I use external burners as the copy burner and my laptop burner as the "source" burner. Keep the copies as dry as possible, and room temperature, OUT of direct sunlight. I also have a 3 tier DVD burner, that does not care for the cheaper disks. Verbatim, Sony, Phillips, Maxwell, etc work better in the machine, with less failures. Just for information wise, the "Smartbuy" brand from WalMart, in both the D5 single layer, and the D9 dual layer, have given me good service. They are made in Vietnam. They, to me, seem almost half again or more in thickness, although I do not know how well, the media stands up over time in holding the recording data. They are usually, about $17 to $20 dollars a hundred disks, spindeless. No spindle, shrink wrapped. You can purchase 100-600-1200 or any quantity actually. To me they seem to be a pretty heavy duty disk. I use them on my external, single burner, or internal laptop burner. This has been my experience over many years of making both CD and DVD copies. Always St.Backup should be with you. NEVER make just one copy, IF you can avoid doing so. Make at least two.
Disks can also be susceptible to mold, etc over time. Coopervid, is quite correct. Listen to him. That is why he said both temp and humidity can contribute to the degradation of the media over time. Treat your main copy and your backups with equal care. Thanks for listening. Please stay safe during the holidays, and the new year to come. May you all have peace.
Louis