I'm going to respectfully disagree with most of the other replies to your question. There isn't much value in maintaining your own engine. All you have to do i

I'm going to respectfully disagree with most of the other replies to your question. There isn't much value in maintaining your own engine. All you have to do is look at the top games made with Unreal 4 and compare to the top games made without it and you'll see it's mostly irrelevant to have your own engine. The tech geeks and engine creators will all claim otherwise but sales and users don't care. They care that the game is fun. Just like in movies they don't care what brand the cameras are, what software was used to render the CGI, what software was used to edit it together. They only care that it's good movie. At last 1/2 of fellow AAA game devs have switched to using a 3rd party engine and so it will likely continue.