Think of the drum of your winch like a gear. The bigger the gear is the faster it turns but the less power it makes - sort of like your old 10-speed bicycle's gears; you shift the front gearset onto a larger diameter gear and you can go faster but it's harder to peddle.
If you were to study the manual on any given winch, it will tell you your maximum rated power - say 9500 lbs - is only achieved when you are on the first layer of rope/cable on the drum. With each extra layer that builds up you are increasing the diameter of the drum (the 'gear') and therefore reducing the amount of load the winch can pull. Meaning if you need to do some heavy pulling you want to be on the first layer of you winch line. If your anchor point is 50' away and you only pull out half of your 100' line you won't have full power available. If you only pull out 1/3 of your 150' line you'll have even less power available. The solution to this is to rig a more complicated design with snatch blocks (which can also help increase pulling power dramatically but takes more time and equipment) or to choose an anchor point further away - assuming one is available.
If you were mostly in the desert or other areas where anchor points can be fewer and further apart having more line on the winch is handy. But in our area we usually have trees or other anchor points within 100' or less so running less line on the winch is more practical. It's also cheaper and easier to maintain. As Brenton pointed out, many of us carry extensions we can use if we need to get to an anchor point further than our 100' line can reach. Extensions can be made up from stuff you already have on hand such as a tow strap, or you can carry a dedicated piece of synthetic line in your recovery bag. I have a 50' 3/8" extension line (haven't had to use it...yet) in my bag and it takes up very little room and weighs next to nothing, so it's easy to have on hand 'just in case'.
If you really want to study up on winching, take a look at the old army recovery manual:
While it's old, much of the info is still applicable. OK-you may not care much about replacing the tread on a tank, but they explain a lot of info about setting up different recoveries as well as drag of different surfaces and tons of other info. Think of it as vehicle recovery 101.
Edited by DHappel, 29 August 2015 - 07:46 AM.