Videotapes are simply put: a plastic tape that contains magnetic particles attached to it. When you record an event, it energizes those magnetic particles on the tape. Videotapes are made to view an event at a later time. The problem is when you want to save those memories for a long period of time. Videotapes can loose the energized particles on the videotape if it does not move for a long period of time.
Now, I don't have the scientific knowledge to back this up, but I can speak from personal experience from seeing this happen over my 20 years in the Video Production industry. It even happened to me before I became educated about the subject. I found my very first TV commercial that I directed back in college. I popped it in my VCR and low and behold, there was nothing there but the sound. No video picture at all.
What happened was that when a videotape does not physically move for a long period of time, the magnetic particles on the tape in which it is wrapped around tend to blend together and get mixed-up.
There are two ways to avoid this situation from happening to you. First, you can simply place your special tapes in your VCR and press Fast-Forward. You don't want to press Fast-Forward if the tape is playing and you can see a picture. This can damage a tape. You should press STOP, then Fast-Forward. You should hear your VCR start to move the tape forward without seeing a picture. This is what I call "exercising your videotapes". You are physically moving the videotape from sitting in the same spot for a long period of time. I recomend that you do this at least once a year to those special videotapes you have.
The second thing you can do to preserve your videotapes is have them converted to DVD. DVD will make a digital copy of the videotape as it is and thus preventing the images from becoming lost. You should put away those special events in a safe place for future viewing such as a safety deposit box or safe. If you are planning on watching the DVD often, consider making a second copy of those "special" videos/DVDs.
Recently, I had a customer bring in a DVD that had been played quite often by her kids. The kids didn't take very good care of the DVD and it became scratched. Once a DVD is scratched deep enough, the DVD may not play properly in your DVD player. People think DVD's are indestructible, but in essence they can become ruined with rough handling or not placing them back in the DVD case and becoming severly scratched.
Here is a recap of what you can do to preserve your special family videos for a lifetime:
1.) You have to be pro-ative and do something to preserve them. Simply just keeping them on the shelf will not preserve them for long periods of time. Do not store them on top of the VCR, TV or Heated source. Heat can damage a videotape.
2). Have them converted to a DVD and make a second copy of anything that you may watch often. Use the second copy and put one away for safe-keeping.
3). Exercise your videotapes of you don't want to convert them to DVD.
