Most of the HKT girls post at least 3 times a day at fixed hours (early morning, late in the afternoon, night time) and most of them have very loaded posts, while girls like Matsuoka and Murashige have shorter posts and a much more frequent rate of posting.
Watanabe Miyuki, being the smart professional that she is, always manages to post at least 7 posts a day, posts videos when she attends handshake events and often interacts with fans by posting a reply to a certain topic that a majority of replies talk about. She also posts before, during and/or after an appearance at a major TV show to explain some things related to what happened in-show.
Yokoyama... well, she really likes her pet cat. Her posts are very short and straight to the point and Takahashi Juri is always there to point out how serious she always sounds (and advises her to use more emoticons). A good percentage of her posts have photos though, which is nice, and she always has good interaction with Takahashi Juri, Kawaei and Shimazaki.
Matsui Rena... she has... varied tastes lol. She has very short posts most of the time with a picture of herself and a random comment like associating Bambi with the word "lifestyle / 生活". She's really passionate about bullet trains, anime and stage plays to name a few, and most of her posts leave fans going "S,sure / お、おう。".
Takahashi Juri and Kawaei Rina often post around the same timeframe and with similar content, and used to post a lot more frequently until they had problems with the Google+ updates and lost their phones on a few occasions. They'd usually post at least once per day at night, but haven't been posting much as of late.
A special mention to Matsui Sakiko for always replying within her posts when she finds responses to react to (which are quite a lot). She always has conversations with fans and is trying to learn English in order to interact with her foreign fans more besides the basic English expressions and greetings.