There really is no real "normal" for the HF-GCS network. Further, what becomes normal changes with time. Coded messages might range from 9 chars (the shortest one I have in my logs, anyway) to over 250. Similarly, there might be more than a dozen transmissions in an hour or there might be less than one.
Listeners like to make a big deal out of certain callsigns, how many times an hour messages are sent, or how many chars are in a message. In reality there just is nothing to be made of these things.
Many messages in a short period might mean something is going on someplace, or it might simply mean they are doing training someplace, and it does not have to be one of the big name announced training exercises. Personally I suspect the only thing that really has any meaning, however small, is exceptionally long messages. I just doubt they will throw padding (extra nonsense information added to a message to obscure it or completely meaningless transmissions sent to foil traffic analysis attempts) on such long messages all that often.
However, I will tell you, sometimes it is also informal "training". Maybe not on the main HF-GCS freqs, but on the discretes I would not be surprised. I once sent a 220 character message in a format similar to the EAMs of today on an Echo Whiskey net in the Pacific. And got a similarly long response in return. I am sure any listeners would have thought "these guys must be talking about something important". What we were passing was details on where to meet and what to do when we got to the PI, because liberty is an important feature in any sailors life.
T!