I have had this noticably for almost a year would be my estimate.
I never have what would be considered severe pain and in the morning does not seem to be much difference. The numbness is more of discomfort and annoying as opposed to painful as my feet generally just have little feeling in the bottoms and especially the balls of my feet and into the toes. Its a bit scary at times especially when barefoot as if i step on something I cannot tell if i penetrate my skin or not?
I can and do walk occasionally and I would say that it is annoying though not greatly painful and I would say it does not improve by walking. I exercise reguraly at the gym and my aerobic exercise is generally down on the eliptical machine.
I had a physical 2 months ago, my doctor said my health was very good. I told her about my feet and she had me tested for lack of vitamin B which I knew was fine as I take multiple vitamins daily. The results came back as fine and now I need to reschedule an appointment.