I had to hire a new assistant last summer, my previous one was with me for ten years, and got a promotion, but it was traumatic to have to replace her. I find that young men are bad to hire, because they are ambitious and you can not keep them, at least I can't. But I hired a bunch of young women 20 years ago, and they are basically all still with me. They all went on maternity leaves, which is a pain, but they all came back at least part-time.
For me, the key to good hiring is to hire from a personal recomendation. Whenever I have hired from an ad, so often they turn out to be deeply flawed, out of work for a reason, with some form of horrible baggage. So I really work my network when I need to fill a position. The new girl was a friend of the daughter of a friend of mine (who I first met when she was dancing and I was her customer). She is great, just like they said she was, just an all around good person. But she may be too ambitious to stay, we'll see.