How long should it normally take for a (hoof) abscess to blow?

7 months ago, my 11 yr old QH mare ran in very lame. After three months of stall rest i was able to ride her for about 45 minutes without any trouble. Soon again, she became very lame. The vet came out and suggested that she was very badly bruised due to pulling her shoes in the fall, coming up lame in october. She suggested iodine and shoeing. We shoed her and then countinued with iodine. After we shoed her she came up extremely lame again. We then decided on x-rays. The x-rays showed a hole in her coffin bone. She was then diagnosed with navicular, which she has no symptoms of. The vet also said she had an abscess ready to blow. We have an idea where the hole came from, and the result being an abscess. What is the time range an abscess normally takes to blow? Under any cirstance. A year? Two weeks?