My house sat vacant for 3 years. The first year I opened the pool it was a literal swamp. There was at least 3 feet of leaves in the bottom. From cover off to crystal clear took 20 days. The first few days were spent vacuuming to waste, refilling, and scooping with a leaf skimmer. The actual slam portion was 16 days.
This year I opened late and it was a swamp. The walls were covered in green and I couldn't see the bottom in the shallow end. It wasn't as bad as it looked since I could see the shallow end bottom after vacuuming. The slam lasted 4 days.
I think most slams are extended due to not getting the organics out before starting and not being able to babysit the pool in the first 18-36 hours. It'll take a lot longer if your filter gets clogged or the chlorine level goes below spam level.
