They say the squeaky wheel gets the grease, but for design firms, freelance writers, designers, and developers the squeaky wheel can take up so much grease that you don't have enough for your other clients. When this happens, it's time to replace the wheel.
If you've been in the business long enough, you've undoubtedly had clients who take up all your time. They constantly call, expect you to return e-mails within the hour, or nitpick at your work until you just wish they would have done it themselves. If they know so much, why did they hire you in the first place?
No one wants to lose business, but it's simple economics that if all of your eggs are in one basket you're on a precarious path. Of course, I don't advocate dropping clients like they're birds on a wire and you're a 14-year-old with a BB gun. First, you need to delicately approach the squeaky wheel and explain why some things take time, or why you did something the way you did. If the squeak persists despite all your efforts, and you begin losing money because you're spending time on “unbillable” endeavors, then it's time for a replacement.
Before you lose your temper (or your rent payment), make sure you have a backup plan. Push your marketing skills to the test to find a replacement wheel BEFORE you cut your squeaky one loose. This way, you won't tip.
If you can't muster the courage to replace a client, start charging for those unbillable hours — either the client will start looking elsewhere for the grease, or they'll pay ... and then you won't mind getting out the grease gun. Of course, some clients simply aren't worth it, and you have to cut 'em loose. You'll feel better, and you'll perform better. Your business will not suffer if you have a replacement wheel.
Do you have any squeaky wheel stories?