This is a good question and one that comes up often. 8mm film can last up to 70 or 80 years if stored properly. It should be stored in a cool dry place. Today they recommend storing your 8mm film in vented cans to allow the gases that build up over time to escape. This can make your 8mm film last longer.
There are two tests you want to perform to see if you can transfer your 8mm film to DVD today. The first test is to take the first 3-4 feet off the 8mm film reel. Try to lay it flat on the table. If the 8mm film lays flat or relatively flat then you pass this test. If the 8mm film is warped and doesn’t want to lay flat, it may just be the first 20-25 feet of the reel. Unroll 20-25 feet and then perform the test again. If it passes the test, then at least some or the majority of 8mm film can be transferred.
The next 8mm film to DVD test is to see how fragile the 8mm film is. If you take about 6 inches of film and hold one end with your left hand and the right end with your right hand. Now, move you hands together pushing the film in the middle up into a loop. This will show how flexible the film is. When you do this, look for any cracking or breaking film and watch the sprocket holes to see if they crack or break as you do this as well. If none of this happens then you pass this test.