My belts were changed 2 years ago and had done just over 1000 since. Its in the garage right now getting its new belts (with the engine out) as well as its valve clearnce/adjustment. The manual says change every 24 months and that is what I go by. I cant argue with what Ferrari says in the manual. If you are in any doubt to when and if the belts were changed then simply change it. Its just better to be safe than sorry.
I'll agree. My Toyota MR2 Turbo has a spring tensioned steel tube for a belt tensioner. It gets replaced with the belts on my car during that service. If Yamaha/Toyota are happy with it I'd say it's a reliable system.