I remember reading somewhere that for a heavy user, average elimination was10 days to cut levels in half? But it will vary for everyone so you need to keep testing. Order some cheap tests from ebay or go to Walmart, cheapest ones I found at around $12 each for THC only.

Check your first void in the morning. I know I came up dirty on first void and then drank 2 glasses of water and got a negative. This was after 24 days clean and heavy daily use for years.

Good luck.