If you can cook it longer, go for it. Keep the flame low. After this much time, the bones and cartiledge will have mostly broken down. You'll want to strain the liquid through some kind of mesh or sieve. The remaining liquid should be thick, rich, warm, and naturally buttery.
Some folks say to skim the fat off.
Do it if you can figure it out. When I have to worry seriously about my arteries, I'll scoop it off the top too. Put all the veggies and soup stock into a large saucepan. Simmer until the vegetables loosen up a bit. You can add some dill and some parsley, the original recipe calls for that.