I think I'm improving, but my performance seems to vary with the weather a lot. I'm not sure if that's normal. Here are my times going off what I recorded on my watch (a few seconds off official time):
May 29, 2016: 2:05:21. It was very pleasant.
August 20, 2016: 2:19:21. It was hot and humid.
November 13, 2016: 1:59:01. It was very cool but not cold.
April 1, 2017: 1:58:03. It was cold but not unseasonably so, maybe 35 degrees.
May 28, 2017: 1:57:50. It was very pleasant.
August 19, 2017: 1:55:59. It was somewhat warm but not hot.
April 7, 2018: 1:49:56. It was cold, 17 degrees, and a very flat course
May 27, 2018: 2:06:08. It was hot, probably the hottest day of the year up to that point.
November 11, 2018: 1:53:56 It was cold, about 30 degrees.
Two hours is the magic number for me for halfs. I'll know I'm past my peak when everything goes well and I come in over two hours.
It is definitely a habit or at least a little addictive. The race experience is so fun and not just because of the medals and T-shirts.