From what I understand you're ok after 6 months or so. If you get it cut too early the hair can actually turn completely silver. You should be ok at 10 months. I think I waited till about 8 to get Maggie clipped.. she needed badly though! Maybe wait to see what someone more experienced has to say.
Also, you might want to search through threads here about what to tell your groomer. I was pretty specific with mine so that I knew how Maggie was going to turn out. I personally do NOT like Maggie's eyes scooped out, so I always have to mention that.