I'm going to throw confusion in here. I've had my Rosemary for YEARS (about 20 or more). It is enormous and bountiful BUT it is kept in a very hot, sandy sheltered south facing garden. They HATE the cold/damp and will often rot in cold winters - they are then unable to cope with pruning. They really need lots of heat, and very good drainage.

You say it gets leggy - there are 2 types you can buy, the prostrate (var. prostrata) version, which will spread and wander everywhere - looks excellent draped off the top of a hot wall, but not so good in a bed!, or you can get a more bushy variety too, which would be better.

We take huge great chucks off ours - big old branches sometimes get clobbered by a passing hose, they are quite brittle. Doesn't seem to mind at all. I guess they just need to like where they are, otherwise they won't be hugely robust.