Touch upâs should be done minimum 4-6 weeks post the initial treatment. This allows time for eyebrows to heal fully before perfecting them for the second time. Free touch-ups are only valid up to 3 months from initial procedure date.
Re: The Tinny sound? Most folks that are concerned about a tinny noise with aluminum boats are referring to the noise generated by the hull moving through the water (which can be modulated/reduced through many different avenues). You mention vibration and rpms, so I'm guessing that you're not referring to that sound.
To an audiophile, 25 pounds of solid billet aluminum around his equipment and blue lights defines sound quality, while the actual amount of copper on the inside, or to what it's connected or what it's doing, is far less important. To an audiophile, the hobby is all about playing with equipment, not enjoying music. A music lover uses the same gear for years or decades. He gets what sounds great, like some electrostatics or whatever, and keeps it nearly forever, thoroughly enjoying to all his new recordings of great acts.