I have some precious home movies which I have backed up as identical MPEG files on a pair of eternal hard drives. But I would like to also copy them to DVD. Then I recalled a claim someone made that movies issued on commercial DVDs have longer life spans because DVD studios "press" the DVDs rather than use computer DVD 'burner" drives. Is this true? If so, than assuming one uses reasonably reliable (Verbatim? Sony?) blank dual-layered DL +/- blank media and burns the disk at a slow (more error free?) speed, what DVD lifespan could one expect, compared to a pressed copy?
Pressed media have a longer lifespan because the reflective layer is aluminum, which doesn't degrade as rapidly as the organic dyes used for a writable DVD.
That having been said, good media such as Taiyo Yuden that's burned with a decently low error rate and stored in a cool dry location should last decades. But you'll never know if the burn is good unless you scan the disc to see what the actual error rates are - you need a burner and software capable of reporting raw error rates for this. I use a LiteOn IHAS424 drive and Nero for this. It's important to check this because burn quality depends on a lot of factors and a bad burn really can degrade in quite a short period of time.
The reality is that ANY media can go bad. The secret to keeping precious files is to (a) have at least two copies, and (b) regularly check both copies to ensure they're readable. If a disc goes bad, this lets you recover the file from the other copy before it goes bad too.
For this reason I dislike DVD as an archival medium since checking that you can still read all of your files means a lot of disk shuffling. It's a lot easier if you use hard drives - you just connect the drive and let it sit there overnight reading files.
For important IE irreplaceable data, I now scan all my DVD burns with PI PO scans using DVD Info Pro. This is after a disastrous event after trying some cheap generic DVD's.
I lost 40ish dvds of data most I was able regain, but some is lost in the ethereal space now. Hey PLEASE return my missing bits PLEASE! Nero was used to verify these burns, and reported as good. I then tried to use them again after 4 months, and they were DEAD! If I don't get 90% DVD burns with a PI-PO media scan on important data I scrap it and try another brand Disc.