I used to get some SERIOUS post-marathon depression. It doesn't help that I have a history of depression either...
For me, the only thing that helped me get out of the "funk" was signing up for another race, and having a new goal to work towards. But I agree that after awhile that the whole racing/training thing can become monotonous too. I am specifically taking a break from marathon-plus distance races this summer to give myself a chance to regroup and just run for the heck of it, not because I think I should be running "x" amount of miles. When I am "training" I often get into a pressure situation where I feel like I need to meet my weekly mileage...which isn't a bad thing when prepping for a big race, but also not why I run. Taking some breaks here and there and even running short races (relatively speaking) is what helps me get out of a funk. Obviously this situation is very different for every runner, but just wanted to share my $0.02!
My Blog: trailsandcocktails.com
I Run for Oiselle
Hyner 50k: 4/18/15
Laurel Highlands 70M: 6/13/15
Lace, I'd be surprised if you DIDN'T feel some sort of burn-out, as busy as your race schedule is. I know that when the Goal race is over I do feel empty. The best way around that for me is to have a recovery race the week or two after as a fun low key step down and transition to the next phase of training. It works for my low key running schedule.
My examples are a 5k on St Patty's day after WTC 50k, and the 3k on July 4th after Western states. Or the group fun run the Wednesday night after the race. These are races I make sure to run with someone slower than I, and HAVE FUN.
I'd say 3 big races a year might be my best racing plan. Although once I have a 50k Base, I regret letting it go.