Quality renders take time, but they are worth the wait. Remember, its not just the time to do the computing, but the effort needed in posing, designing, staging, detailing and even photo-shopping and post-production. They are the life of the party though.
Next up is writing, it takes time, effort and the ability to criticize yourself, rewrite and improve. This one will vary based on experience but it'll always take some significant time... as long as you treat it with respect and care about it.
Code is not a time eating thing but we're both originally programmers her at
beWilder so that might just be us. It depends on your codebase, if it is complex or if you are using a mostly prebuilt engine but in general it should only take a small amount of time to work in content updates once the main game loop is functioning as needed.
Audio is the dark horse... you really have to do it all or do non of it, nd most people do the latter. It takes much more time and effort to do than you'll ever account for unless its something you do every day and can truly estimate it well. This could potentially overtake writing as your next time consuming task.
Hope that helps!
Edit: This is a good example of the work that should go into your renders if you want them to be the best they can be. This this kind of detail that eats up the time and is often overlooked. Tell me it's not worth it though...