There are two reasons to track time:
- Timing (duh): Seriously, the timing of disparate movements so that their individual effects on the battle as a whole can be understood. If you have a unit of cavalry attempting to sneak around a small grove of trees and make a flank attack, it is vital to understand the state of the battle when they complete their movement and launch their attack. It is also important to understand when effects become active and when they no longer apply.
- Movement: It can be important to know how far a character/creature can move in a specified amount of time. Or, more to the point, how long it takes a character/creature to cover a given amount of space.
I've never been happy with the idea that a combat can last 10 minutes or more. That is a lot of work to swing a weapon weighing 8 lbs or more, virtually continuously. The lack of fatigue rules makes it worse.
I think time and movement should be abstracted the way the rest of combat is. For time, I am thinking about randomly determining elapsed time. Maybe roll d4, +1 per HD of opponents in excess of characters' level. So, a 2nd level fighting-man, a 1st level fighting-man, and a 2nd level magic-user engage a group of 7 orcs. At the conclusion of the battle, roll d4+2 to determine how long the battle lasted.
Wandering monsters being attracted to the noise of a battle can be checked after a certain number of exchanges in the fight. I would likely just judge the progress of the battle. If the battle seems to be dragging, I would avoid wandering monsters like a plague. If they would add some spice to the session, I'd roll for them.
When you take away time, you take away movement. At least in the sense of covering distance in time. I like the idea of Arenas from Old School Hack. I can see them having a place in a more abstract time keeping scheme. It's a fairly simple concept and I think it really lends itself to exciting, swashbuckling combat. More importantly, movement in the system doesn't rely on accurate time keeping.