If you share with your vet that you're testing regularly, and share a copy of your numbers, they may be more receptive to refilling the script without a visit. Mine comes from Walgreens, so there's a script for about a years worth there; ProZinc you pretty much can only get at the vet's office. Some vets like weekly or monthly updates. I actually took my vet to lunch, shared boatloads of info (highlighted), links to various websites, and other things.
We're also in regularly enough with the rest of my gang, that she knows if there's something going on, I'm there. But honestly, having a partnership with your vet is the best possible way to manage FD. They do need to be a part, but likewise, you need to let them know that you're not a passive owner - you ARE the primary care-giver. And ultimately, you hold the needle; you decide what to shoot; you are the responsible one.
Hopefully they'll be receptive. It's often helpful to have your questions for the vet written down - or better yet, e-mail to them in advance, so they can be prepared to respond. And be sure not to step on their toes... we all know that they spent more time in vet school than most of the rest of us!
Good luck!