I am in the market for a replacement frame and during my internet searches I keep reading the term "fatigue" when I am reading about aluminum frames. What is up with that? Do AL frames really only last 3-4 years now? I rode my last aluminum road frame for 8 years plus and never even thought about fatigue. I then sold it and it is probably still out there on the road. Is this a problem only with the super light AL? It is hard to justify an AL frame if I feel the need to replace it every 3-4 years which seems to be the number that keeps coming up. How can you tell if the frame is fatigued? My last frame never looked any different or rode any different after all that time. It would be silly to buy a used AL frame if it were more than a couple of years old if this really is an issue. Somebody please set me straight.