He spent 300 years waiting for the Tardis to return the first time (when Clara was hanging on to the key and the Tardis dragged her along) BUT the doctor tricked her again and he spent some more time defending Christmas and aging along the way until Tasha Lem went back to fetch Clara.

I'm not sure he spent a century, but he's got to have spent way more than 300 years in Trenzalore.