Here's an excellent page on the topic:
While the author focuses on a one-year gap, my understanding is the NCAA D1 rules wouldn't be different if it was a 10 year gap.
In reality, and in the sport of tennis, it would be almost unheard of for a D1 program to be interested in a guy who hasn't played competitive tennis in 10 years.... even as the author explains, 8-months of no competition can be an issue with coaches.
But yes, as in football, a 27 year old kid could play D1 tennis if not playing competitively after HS (or only three years anyway.) And obviously I haven't had first-hand experience in doing so.