Paddocks are considered "low worm-risk" when over 90% of the worms on them have died, and further contamination with worm eggs has not occurred. This generally takes 3–6 months (depending on the temperatures at the time). However, in some environments, most worm larvae will die once temperatures have been extremely hot for a few weeks.
Surveys show many people are in favour of preparing low worm-risk paddocks but most of them are unaware how long is needed.
More information on preparing low worm-risk paddocks can be found here: Grazing management
or the specific recommendations for your region are found in your regional Worm Control Program.