It's obvious that the brand of blank DVDs makes a difference, but what few know is using a *slower* burn speed, such as 4X, can greatly help.
Some other suggestions:
* Be sure no extra programs, browsers, etc are running when burning - if not possible, consider getting a dedicated computer just for burning use.
* Make at least two copies using two different brands of DVD - and on each DVD itself, burn two copies - that will limit data to about 2.2 GIG per DVD, so not always practical for video, but certainly worth doing for pictures.
* Storage - keep in dark, well ventilated place - not the garage nor the attic. Keep moisture under 50% whenever possible.
DVDs can be a good intermediate backup option that can with some care in burning and storage, likely last 10-20 year, and perhaps far longer - no one really knows yet.
I remember back when consumer grade videotapes became widely available some people claiming they'd only last 10 years - and yet roughly 30 years later, it turns out videotape degrade somewhat, but nowhere near as much as was once believed. So it's quite possible in 30+ years burned DVDs may still be readable with little to no data loss.