Yes and no. If you are doing what you can to pull out wins, and lack talent, then I say let them stay. Sometimes longevity is beneficial for a program, especially one that needs consistency. If it is an established program and it going through a "rough phase" then give them some time (i.e. 3-4 years) to get the program up. Basically it is like teaching, you get 4 years to prove you are tenure worthy. If you aren't then, you get the ax in your 4th year.