Loose-schooling is something I don't normally do as I have no suitable area. In our household it is, therefore, the term used for when you can't catch the blasted horse and decide that instead of them making you chase all over the field you will stand in the middle and crack a lunge whip and get them some exercise that way.
Long-reining can be useful at various stages of a horse's education/life.
Benefits can include, and are not restricted to, learning how the bit feels in the mouth and understanding directional aids, desensitisation and direction training for driving horses, exercise of small ponies by adults, exercise where the horse can't be ridden for whatever reason (illness, damage to back, tendons etc).
When our big mare begins to come back into work after her ruptured tendon I will probably use her walking time to long rein her and get her accustomed to driving harness - killing three birds with one stone in case she's never fit for her previous intended career of eventing.
& Excellent for re-hab as can work horse low and low in straight line without the weight of a rider.
*Dressage training, if you are proficient at long reining then all lateral moves can be trained, practised and performed on long reins.
*Good for teaching a young horse aids, and also means an unback horse can be educated out round fields and quiet lanes (not sure if it's done so much now, but everyone who back a youngster when I was a child, used to long line them out round bridleways and lanes, as part of their ground work, before they back them).
*Inital training for harness work.
Loose Schooling
*Bit of fun for the horses.
*Useful for schooling horses over jumps, so they learn to think for themselves, without the interferance of a rider.
I loose school Beau every few weeks, and some times if I only ride for say 20 mins I will do it for a bit after. We go over voice commands and I find it good for seeing how he is moving - watching his muscles etc. I also find it good for stretching him out.
We have only a few times included jumps, and he was never forced over them, and he would have 3 different heights and he would pick which he wanted to do - and he would often end up just turning and going at the jump himself.
I have never tried long reining tho, as I do not fully see how it works other than for providing instruction as to speed and direction more than lunging.
we never lunge a youngster as the strain it puts on its joints, we long rein them as they see the world and they have to learn to go forward out of the yard on its own.
we loose school them to get any steam out of the horses when they have been shut in or before we ride them, we also loose school them when were showing off their paces to customers