To me this is just not a "computers' power" issue... It is a logical issue - that battles that last a long time aren't placed in a limbo out of the world, but it's normal that after a while both defenders and attackers have their reinforcements arrive, and need to reorganize.
For the battle's timing too, 50 seem a lot, and just right. I mean, after 3 turns waiting, the most of the troops need to attack or retreat. That's maybe one turn to reach the enemy and then 44 to bash each other. It doesn't seem so restrictive.
I just would like someone to tell me what can an upper turn limit add to the game experience - actually, I see no advantage. While the things as they are have the advantage are:
-low-systems friendly for no long waits
-logical for the needs of the armies to reorganize
-a balance issue as the troops you have in the proximities of the battle (near provinces) should be able to join the fight after some time.
Really, why do you ask for an upper turn limit?
Even an adjustable issue - I dunno. Wouldn't that create a lot of confusion for the MP games? I mean, having battles ending at 50 turns or at 200 goes for a ground-breaking change in gameplay. Deciding a turn limit for every MP game, while many adjusts it in SP the way they like, could end up being uncomfortable for people used to different battle tactics.
I don't wanna do destructive criticism for that. I would like someone explaining me the point, if there is any.
Peace