Even so, it still might be possible that you have the deficiency. If you're taking the B12 in the form of cyanocobalamin, many of us can't convert that into the active B12s we can actually use and absorb; it's a very inactive form but the most common one used. If you're taking B12 in the form of hydroxycobalamin, that's a bit more active, but still has to be converted into a usable form by the body - and many of us can't do that. In the case of folic acid, that's another form that needs to be converted and may not be; methylfolate is the active form.
Because we have more trouble than the general population converting inactive forms of vitamins, if you are treating for methylation using these forms, you may still not be getting enough B12. In fact, taking inactive vitamin forms sometimes blocks the receptors for the active forms, so you get nothing at all. High blood (serum) counts of B12 tend to indicate not that you have a lot of B12 in your system, but that it's swimming around in your bloodstream because it's not landing on the receptors properly. The only way people with neuro problems can accurately measure B12 levels is in the cerebral spinal fluid.
This is sort of the babyspeak version of some of the stuff I have learned on the "Hidden Story" B12 protocol thread. There's a lot to be learned about methylation and B12 deficiencies. Some think this protocol is too drastic, but while I don't enjoy startup symptoms, I can really really feel the progress after 4 months. I'm wondering if this years-long methylation treatment is having noticeable effects for you?