I've found that when they are braided they tend to break off more hair when they rub on something, so no advice there.
I have working QH's with manes to/past their shoulders. I use jojoba oil to condition (I get it by the gallon from Solid Gold in CA, fairly expensive but lasts a long time! I use it on myself too) I try to keep them worked through on a regular basis, no metal combs of any kind and usually just finger comb them to prevent breakage.
You might try MTG to get some growth going. The stuff works wonders but smells like a smokehouse. I use it on broodmares that have had their tails used for pacifiers. Had one chewed off to above her hocks last year (despite trying cayenne, listerine, sour apple, darn babies!) and it's to her fetlocks now, I used MTG every other week on her.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.