Since you just had gamma knife this year in May for a tumor that grew back, going every other year at this point I believe is too soon. I recommend you try to find (if possible) another doctor, even if it is not a neurosurgeon if that doctor is willing to order the yearly for a while until you are feeling more comfortable about stability of the tumor.
It was a few years, I believe before my parent with a meningioma went from yearly to every other year for MRI check ups after gamma knife. The tumor shrank and then pretty much remains the same size with recent scan results.
In my opinion I would wait as they suggested.
Given your history, your headaches and all... in your place I would be kicking and screaming as well.
It is great that the gamma shrunk the tumor - but there can be side effects from the gamma (necrosis among other things) so going at this point to 2 years would not make me happy. I would still want an annual. Your hubs, sadly, has only supported the docs and never you (if he ever gets sick with something out of the box, gee, wonder if his tune would change?). The tumor is not gone yet - it is, as I read it, still there just finally stabilizing and reducing. It is going to take time. We are long term patients.
On the other hand, it is great that you are starting to feel better. After I got a bit stable, I got down to a lesser weight, but never my before weight - and I am now on an extreme diet to try to pull it down and it is making me cranky. Plus my overweight hubs does not want to diet and he needs it as much so ugh...
Take care and try to hang in there- and when a year comes around, see if you can get someone to push for an MRI if you feel you need one.