Wow, Joel. That’s a long ways to come! I don’t think you’ll be disappointed, that’s for sure!
I chose March because, outside of it being my birthday, I wanted to make sure I had plenty of time to reach Katahdin while still being able to enjoy the trail and all it has to offer. If, technically, Katahdin closes on October 15th, I’ve given myself a good eight months to get there. However, there’s always the possibility of it closing sooner, too, depending on the weather. I guess I’d rather put up with a little snow at the beginning of my trip and know I can make it rather than waiting for better weather to start and possibly having bad weather cause me to not finish. 
A-KA