I have a 8-10 year old Tormek (approx) with the original wheel. I never let it sit in the water after using it. Lately, I seem to be getting a dip in the middle of the stone that develops after sharpening just one or two HSS bowl gouges - sharpening, not re-shaping. Reconditioning the wheel between gouges helps some, but I feel like the stone has become "soft". Could this happen after a number of years? If I replace the wheel, which replacement do you recommend for HSS gouges?