Why does the military adviser stop giving me advice midway through a game?

Anytime I get about midway through a game of Civilization V, the military advisor stops giving me information about how strong most of my opponents are. That is, at the start of the game he will say something like:

The Ottomans wield an empire that could wipe us off the face of the planet

or

The Chinese aren't quite as strong as us militarily

He will initially provide this information about each other player. This is useful information, but later in the game he only provides it for some other players, not all. Why is this? Also, what determines when he will stop providing this information?

I loaded up a few old games, and in several of them my military adviser was informing me of the comparative military strength of other nations. In one in particular, I was deep into the Modern Era, and late in the game, and he was still warning me about the might of the English army.

I don't know what the algorithm is specifically, but I believe advisers only provide information that is noteworthy. In your case, it may be that as time passes, you and the other nations are reasonably matched by whatever criteria that is used to determine if the military adviser will take notice.

As time passes in the game, weaker civilizations are often wiped out in wars with their larger neighbors. It's possible that surviving into the late game means that your military is comparable to others, so there's not much for the adviser to comment on.