You can not predict the success of a product as the market is insanely unpredictable. It is really great your so well settled at your age but you’ve a lot to learn about how the game works bro. I hope you sell a trillion copies but as I said I have seen insanely talented people with amazing products fail.
as for the original poster, 28 is young man, In my computer science class the average age was 38 years old. if you was 50 id say start worrying a bit lol