If you tension your heads quite tight, you won't need to adjust them as frequently. If you tune medium to loose, you will need to adjust tension/tuning more frequently, even between songs during a set.Thoughts?
You re-tune when the drum is no longer tensioned right or when it sounds "off". If you strike the drum with more force, this will happen more frequently. It is also exacerbated by tension rods which have a lot or very little lubrication.