>>2000133Private usually takes the longest because you're going from knowing nothing (and sometimes having to unlearn habits from things like vidya) to performing maneuvers within specified parameters. There is a LOT of material to go over, from flight controls to airspace to instrument operating principles.The average person takes a little under a year to go from zero to private, obviously that's skewed with more part-time and hobby fliers than full-time career changers but you should still budget for 6-8mos with scheduling DPE's and bad weather in the winter.
Instruments is more technical, you're going from S-turns across a road and short field landings to briefing plates and flying SIDs, but the actual FLYING isn't that difficult, if you can maintain a heading or a specified climb/descent speed, it's just a lot more rules and regulations to memorize and a different way of thinking about flying
Commercial you're going back to VFR and you're performing a lot of similar maneuvers to private, but to tighter standards or with different parameters, and you're expected to know the regulations for offering your services as a pilot which you become legally able to do.
>>2000135is right, ab inito to CFI/banner towing/pipeline patrol should take the average person about 18mos
