I have finished my scanning project, all 165,873 pages of it.

I will be giving the files to my client on a portable USB hard drive, and will encourage her to copy the hard drive to her own computer (which she hopefully backs up occasionally) and then put the portable drive in a safe deposit box or someplace off site.

Additionally, I have burned the data onto a set of DVD-R discs to be kept in reserve as a last-ditch, desperation recovery option.

How long will these DVD-Rs retain their data integrity?

How long will the external USB hard drive retain data integrity?

Assume that both will be kept in reasonable storage conditions.

tanstaafl.