Keep ya'tapes.
They might look a bit scratchy in years to come, but they'll out last DVD
Yes, but not by a great deal!
Home VHS tapes, of good initial quality, properly stored should last (as recorded, without data loss) 10-15 years, 20 if you are lucky. DVD WORM about 8-10, although this is still based on largely on accelerated testing than actual elapsed time.
Good quality 35mm polyester-based cine film stock or still negatives (remember those?) are expected to last 100s of years.
I can't help thinking we are sacrificing longevity for the sake of storage density and convenience.
SD