It’s all depending on how often you feed each head. We feed them once a day with shrimp from the market and each large head can consume 1/4" of a shrimp easily.
We started out with 3 heads and within the first 6 months of daily feeding no sign of any babies, it did grow bigger though. After 6 months we saw a few small babies, in about 2 years we got about 20 totals and now it's a mini colony, one a month is feasible however, growing out the babies takes forever.