My answer will probably give some of you anxiety. To answer the original question of how many in current rotation, I'd venture a guess of 100. I have somewhere between 400-500 jars of blends. The jars I gravitate to are in my "tuhbaccy station" and the rest are pushed aside and receive little to no attention unless I am revisiting a blend or decide to mix a tobacco cocktail.
Of those 100, weather/temperature divides them into latakia blends/non-latakia blends. I don't enjoy smoking latakia in warm weather and Arizona is warm most of the year.
Beyond that, it's all about mood. Sometimes I know exactly what I feel like smoking, sometimes I don't. I'll pull out jars and starting giving them a whiff. Am I in the mood for a lakeland today? Something light and airy? A punchy vaper? A strong virginia burley? I may only revisit the same blend 2 or 3 times in a year currently and I smoke almost daily.
As time has gone on my buying habits have definitely focused in on a smaller amount of blends and continues to trend that direction. I could probably be happy with 40-50 blends. I do like variety because I'm not in the same mood every day.