My horse had an abscess a couple months ago, she was never lame. I arrived one morning and her leg up to the hock was swollen, I poked a bit at the hoof and out came the puss. The swelling was gone by the next day, I soaked the hoof a couple days, kept the hole clean etc, and we were riding a couple days after. I think it pretty much completely drained that first day, nothing else seemed to come out with further soaking and poulticing, but better safe.
I think I'm fighting a rather deep abscess right now in my horse. He showed signs of it 2 weeks ago. Called the vet out and found a sensitive spot, so we packed his hoof and put him on antibiotics. He was perfectly sound 2 days later and has been for 2 weeks up until last night. It never blew out. So I packed it again last night and put him back on antibiotics (left over from last time).
I'm not sure what else I can do right now. He has some surface cracks that the vet thought might be exacerbating the situation. Farrier is due in 2 weeks, so I think I'm going to talk to the farrier about putting on shoes. The only common denominator in all this is the wet weather.