With new pirates I'll usually add a couple to my collection, customising the extra one. There's no desire for uniformity in pirates, so I don't want many.
For uniformed militaristic figures like soldiers and knights, I'll buy 1-20, depending on their looks. I don't want to build huge warmongering armies, just a unit I can use to man a watchtower or attend a jousting convention.
For Police, Hospital and Firemen, as they're not my main themes, I'm generally ignoring the new releases. I might add a Special like the SWAT Officer, but my existing units are good enough to do a photostory or just play with.
The new Western sets, when they arrive, will be tricky. I already have banks, stagecoaches and Sheriffs' offices coming out of my ears so there's nothing there I need or particularly want. The figures are just figures, nothing special.
On a slight tangent, What I'd like to see in a new Western release is a log cabin for foresters and people who live out of town, a ranch for a cattle baron, and a generic town building which could be used for a store, undertaker, doctor, barber, newspaper office, blacksmith etc., i.e. all those things that collect and prosper in a town, or just people who live on main street. I might be able to adjust the carry along bank/sheriff's office to do these jobs, but it'd be nicer if Playmobil recognised the need for them and created the necessary signs and accessories.