If you look at 2016, they never staked in Nov/Dec (and July IIRC), which would carry over into 2017.
I'm not near a PC right now, but if you have the chance I would suggest averaging the daily earned over a 36 month period. I would expect it to average out to (I think?) ~1k a day.
RE: Questions that keep buzzing in my head about GridCoin Staking