Both players must have spent dozens or more hours learning how to engage in intricate cardblocks/evasions for a board game made originally to be played casually. And then, to employ those skills over hours in a completely meaningless game merely to "win".

The average age of players is remarkably high at that level, so its likely two 35+ year old men are playing each other.

(http://www.autoadmit.com/thread.php?thread_id=5662031&forum_id=2#48539821)

The ONLY way a two player game can stalemate is if both players were dumb enough to leave their main armies trapped behind their own territories, but your post implies that we are talking about experienced players. At that point, if they are playing under rules that limit how many armies can be "moved" per turn, one player could continuously attack the moved armies down to 1, but not take the territory, and that would keep a large accumulation of usable armies from happening. The only time this would make sense is if the boxed-in player has more armies, but the attacker is getting more armies per turn. I haven't ever seen this happen for hours though. The player on the losing end of the attrition will concede.

(http://www.autoadmit.com/thread.php?thread_id=5662031&forum_id=2#48539915)

this is also more likely when there is a large bot (5k+ troops) occupying 1/3rd of the board and too big to kill.

if you are experienced in playing fixed cards then your post makes sense, even normal progressive makes my scenario impossible, so add capitals (3 defending dice) and if you play the current Risk my situation is also slightly more likely with true random dice rather than balanced blitz.

(http://www.autoadmit.com/thread.php?thread_id=5662031&forum_id=2#48539947)

here you can watch a most of a 3 hour game that turned int a multi-party stalemate

https://www.twitch.tv/videos/2312558273

the elegance of this video is the use of a bot card farm by blue. he later moves troops to force the other bot into slamming 3k troops into the player that held 90% of the map.

(http://www.autoadmit.com/thread.php?thread_id=5662031&forum_id=2#48539982)