My garters, at least the '07 ones, get one 1.5-2 gram pinkie twice a week. Right now, that's about 10% of their body weight. All my snakes seem constantly hungry these days, so over-feeding is definitely something I'm looking out for. I fed the adult just a couple of hours ago, but she has already started cruising in front of the door when she sees me. The feeding responses I've been seeing this last month, have been insane. They get absolutely hyper when it's feeding time, the twins are even striking at the tongs now and the adult doesn't seem to connect the smell of food with the actual food items, she just blasts past them when she comes up to investigate. edit: I'm trying to rephrase the last sentence so that it doesn't seem like there's something wrong and she's trying to escape.
I'm prepared to bet my left nut that it's a feeding response. She only gets that way when it's feeding time and I doubt she's just excited to see me.
Then again, I have no idea how all your garters behave at feeding time. Maybe my snakes have been abnormally calm until now.