This is a very broad question that basically amounts to "how should matches play out?" It generalizes the questions of how long should matches last? and how, if at all, should matches forcibly end? It also strongly relates to the question of offense versus defense.
The pacing of the game describes the cadence of actions that teams engage in from the beginning of a match to its end. The game is free to influence this cadence by changing things throughout the game (e.g. a system like Tremulous's stages, in which early stages provide mostly defensive benefits and later stages provide mostly offensive benefits). I described a broad categorization of actions in this post, namely: active offense, passive offense, active defense, and passive defense. So this question can be reduced to: when should each of these actions be appropriate and encouraged by the structure of the game? I realize this will be hard to answer without making assumptions about what specific mechanics the game will include, but those specifics can't really be decided on without knowing the purpose they serve regarding game flow. So I recommend people answer this by imagining what "phases" matches should go through.
A simple example:
Beginning: Teams establish footholds across the map either conservatively (mostly passive defense) or aggressively (mostly passive offense)
Mid-game: Teams have established the minimum amount of defensive structures they're comfortable with and start attacking and positioning themselves (active and passive offense), and don't defend their positions too strenuously because there are still resources up for grabs.
End game: The map's resources are now almost entirely under the control of one or the other team, and the two teams must start attacking in earnest in order to advance (active offense) and must also actively defend their gains in order to not fall behind.
A more complex example might include estimated durations for each phase of gameplay, and include mechanics for more explicit transitions between (stages, for example).