Well, the year is a guideline. It is more accurately described as maximum medical benefit. They can't really judge you unfit if there is a good chance a different treatment plan will make you fit. Remember, being unfit is a negative finding, they are saying there is no way the military can work with your condition. So after that second LIMDU the doc couldn't waive you to keep trying different options, the MTF commander or MEB folks can.
What they want to see is the doc talking about the different preventive meds you've tried and why they are out of options for further treatment with those. They also want to see the different abortive meds you've tried and why they are out of options for further treatment with those.
Example:
Tried topomax and it reduced migraine frequency, but side effects couldn't be tolerated
Tried anti-depressant, no effect
Tried blood pressure med, moderate effect, currently at highest dose that can be safely tried
Tried imitrex, was no effective at aborting migraines
Tried relpax, is able to abort migraines, but not until second dose on many occasions, and the symptoms while waiting for meds interferes with work.
There are lots of treatment options, some won't work, some won't be right for you due to drug interaction, etc., and some will work, but just not well enough to make you fit to serve. They need to give you the benefit of the doubt that you can serve until every option is exhausted. Sometimes this is you being more aggressive with treatment providers about trying new things, sometimes this is simply a matter of the provider documenting things better.
Your next course of action is to keep exploring options until the provider submits you for a MEB again because nothing is working well enough.