Measure your satisfaction? Tell you about new products or styles that may benefit your hair? Offer new ideas? If not, then it may be time for a fresh change. Ask first if you think the relationship can be enhanced - if it's important for you to discuss your style before getting it cut/colored, then ask. If you weren't happy with your last visit, communicate why not. And if all else fails, try a consultation with a new stylist, then head back to your first stylist with those fresh ideas. Who knows? You may avert a breakup. If your relationship is beyond repair, then by all means, make a change. But it's courteous to send a polite email or letter explaining to your former stylist why you switched to avoid any awkwardness later.