Quince - those are like apples or pears, aren't they? It shouldn't take nearly that long to finish getting the juice out of them. I would suggest washing them then cutting them in half and setting the halves cut-side down. And after about 30-40 minutes you should have as much as you're going to get.

The test is the hose. Don't leave the cover on the end of the hose, and leave it propped up on one of the upper pan handles so nothing runs out accidentally. When you notice some juice beginning to fill into the bottom end of the hose, then set your collection jar in front of you (I use a stool a bit lower than the stove top with a quart or 2 quart jar, usually) and tip the hose into the jar. Be careful not to over-top the jar - use the clamp if you need to or just lift the hose till it isn't siphoning any more. You should be getting juice after about 20-30 minutes over the boiling water and after you've decanted from the collection pan a few times it should slow to a stop. That's when it's finished. Let it stand a little while and there might be a little more juice that dripped into the pan that you can pour off, but only touch the fruit in top once you have finished decanting the juice.