How long does it take for villagers to breed?

I've built an underground iron golem farm (making sure every door in the village has one block to the outside that is lit by the sunlight), and have cured 2 zombie villagers. I've put them in the chamber and awaited.

I'm at the tenth day (2 hour and 30 minutes+) since they began showing hearts on their head and they still haven't bred.

Q: What's the minimum and maximum required time for them to breed (assuming 48 doors/houses are provided)? Is there anyway to speed the process up?

I've tried taking a brief look at the villager minecraft wiki page but I couldn't find any information.

Solution 1:

If villagers are emitting hearts, then you've done all you could for them. Now it is only a matter of them entering love mode simultaneously, which is entirely in the hands of God of Random.

I've been frustrated with my villagers not mating once, too. You can't do anything, regrettably. Just ensure your villagers can meet easily once they want to and wait - possibly find yourself something to do nearby.