Good evening fellow Kanonians.. (what do you call a Kano pool member anyway?)

As you may remember (or likely not because I'm not that interesting) I had 3 S9's plugged into our pool 3 weeks ago. Increased to 5 today, and a 6th one to be plugged in tomorrow.

Of the five S9's presently plugged in, four of them show May 2017, and one of them Dec 2016 in the main status page of the miner.

Which leads me to my question regarding firmware.

The four of them have two each, 2.47 and 2.52. The December unit shows 2.32.

Is there a preferred version that "works best" with our pool? Is it a good idea to update to latest version? Anything to avoid? Best practices for updating?

Thank you in advance for your time and replies, found lots of dated info when I attempted to search.