Over 35 is common, and in my opinion BS. Isn't Chad Reed 35 this year?!
If the clubs want more of us over 50s to race, and I wish they did, they need to raise the age a bit.
Their seemed to be plenty of Vets in the older classes when they ran a MX "Vets Cup" years ago.
Last year at the Australian Supermoto championships they had a good field in the over 50s. This year we had to race with 35yos.