Lhermitte's CAN be an early sign of MS but I think more often people have something else as a first sign, such as optic neuritis, numbness, or trigeminal neuralgia
LOTS of people with MS are very mildly affected and never have significant disability through their life. Lots of people are walking around with it and don't even know it and never will (as shown by autopsy studies). Most people remain able to walk all their life.
For most people, getting a diagnosis is not all that lengthy.