there are a couple of reasons why there is variation
the first and foremost you nailed on the head, the insurance company limits the number of blocks allowed so the doctor is forced to inject the patient then see how long their improvement lasts. which leads me to my next reason, the most significant factor in the time difference among patient response. some patients can have a block and feel better for almost a month, others like myself walk out of the procedure feeling great but within 4-5 days the effects wear off so i have to have a block once a week. a third difference involves the doctors philosophy on treatment, some doctors wait until the patient is in unbareable pain before they schedule a block, other doctors (like mine) feel that it is better to be aggressive in their treatment and thus do blocks with far more regularity.
we have a perfect example of the differences in physician philosophy in my area. there are two anesthesiologists in the practice, 1 is very aggressive and does blocks on his patients often, the other is more conservative and chooses to do blocks only after all other treatment options have failed. they actually manage to cover a large number of patients and everyone is happy. they have patients fill out an initial interview questionare and decide which doc is appropriate. if after treating the patient for a while it is determined that the patient would get better/more comfortable care from the other doctor the next time the patient comes in they are given an extra 30 min for them to sit down with both docs to discuss what they are thinking. most patients agree and willingly switch, others when presented the options decide that for whatever reason they are with the doctor they feel comfortable with and they remain patients of their original doctor. when presented with the distinctions among the physicians patients usually immediatly know whom they feel more comfortable with so it works.

HI THERE,
Many thanks for posting this. I ive in the UK so things work different to America. In England we don't need insurance, we pay about £200 to the goverment every month and that money goes towards medication, schools etc. However we need insurance when we go on vacation (holiday) Your post was really interesting.
I really hope that you are feeling better
Love
Alison
((hugs))