Keeping Good Associates

It takes awhile to train new associates and techs and then it seems like just as soon as they're at the top of their game, they leave and go somewhere else or quit to have a family or move to a new city. People just don't stay in the same jobs as long as they used to and it's frustrating to have to invest in people who are just going to leave eventually anyway. Because I'm picky, I want "the best" staff...but keeping these people for a long period of time is tricky because they want higher salaries and they are more demanding about shifts, etc. I'm not sure how to stop turnover other than hiring people who are less desirable (which I obviously don't want to do).