In answer to your question regarding the frequency of splitting, it seems to depend on the anemone and also on conditions. Some BTA's seem to clone more frequently than others regardless of conditions, and most will clone when some stressful event occurs. If you research, you will find articles on ways that people prep their anemones to elicit assexual reproduction. For instance, no water changes for weeks, regular feeding every few days for a couple of weeks leading up to the water change, and then a 50% water change.
I personally just let them clone when they will.