I do the same as bob, I use the 'alt' key to make sure they don't use the plium, especially if i have a few units in the same area, IMHO the use of the plium is outweighed a lot of the time by the fact that they don't get an effective charge if they use them (unless the enemy you are attacking is just sat there doing nothing). I wouldn't put them onto fire at will either. From what i have seen, on fire at will, if they break an enemy, rather than pursue them they throw plium at them first. So say 2-3 men survive to flee and then run through another unit of yours to escape they then get 100+ plium thrown at them most of which end up in your own mens backs.