Option To disable the Real-time Learning
To disable the Real-time learning go to Warden -> Settings -> Learning Settings -> Sieve learning -> uncheck Use IMAP sieve learning and save the page. When the real-time learning is disabled. Then you can schedule nightly training instead.
Using the Command Line Interface
// turn off the real-time learning
warden --task=antispam:sievelearning --use_sieve_learning=0 --reload=yes
Enable Scheduled Training
Go to Warden -> Settings -> Training Settings and schedule nightly training instead.
Using the Command Line Interface
// set the training to daily at 3:00 AM
warden --task=antispam:training --training_interval=daily --training_hour=3