Nope. Don't be greedy.

I have a client who loves something I made around 7 years ago as well, and he gives me a huge chunk of the revenue now because I've been helping him maintain it and modify it to fit new clients.

He's a good friend now. He said I do have a family and he didn't feel right paying me so little when others were charging him 20x the price or so. So he offered the fairer deal.

It's not right to change your rates years later. However, since you have the high ground here, use it to propose a new deal where you add new features for a cut of the profits.