Video tapes are an analog medium, and, much like vinyl records, the images are physically stored on the medium. Over time, the tapes degrade, even if unused. In as little as 8-10 years, the tapes can suffer significant degradation; a tape's total expected lifetime is less than 20 years, which is certainly not what you had intended when you made all those tapes!

The primary problem with video tapes is that the binder, which holds the magnetic particles to the plastic tape, weakens over time, and the particles come off the tape. As the magnetic particles come off the tape, two things happen. First, the color and audio start to fade and deform...you will see color shift and hear changes in the audio. Second, the timing and color burst signals on the tape, which the VCR picks up and uses to re-assemble your picture, also start to fade. Straight lines no longer look straight, wavy, rolling lines start to appear up and down your picture, and your picture starts to jitter as your VCR starts to have trouble picking up the necessary signals from your tape.

In addition, the physical tape medium degrades. This degradation can appear as up and down jittering as the VCR loses it's ability to track the signal on the tape.

All of these factors combine to eventually make the tape unwatchable, and your videos are gone. :-(