if you're posting about yourself the fact that you're considering it suggests you're not 'too old'. It can be quite tiring but not really that demanding in a normal road car, gets a lot of adreneline going though. It's only a trackday at the end of the day, do open pitlane and you can drive as much as you feel like. It is mostly younger people doing trackdays though, there seems to be more older people competing in motorsport events