Microneedling needle depth

What in your opinion would be the ideal needle depth and frequency? Every two weeks? 

I am not an expert on microneedling; however, it makes sense that needle depth should be 1-1.5 mm to reach through the epidermis and impact the stem cells which are found high in the dermis. The frequency is purely an intellectual guess. I am seeing that many of the Reddit posters are doing it weekly which sounds ok to me. I am certain that once a hair cycle has passed, the growth from microneedling will be undone unless more microneedling is performed.