One possibility that suggests itself in this arena would be to adopt the "limited shots" paradigm per turret (before needing to reload from outside the turret) mechanic for missiles and sand.
The "limited shots" paradigm for missiles and sand is that each weapon installed into a turret has "3 shots" per weapon ... and the turret itself can store an additional 12 shots (divided amongst all weapons installed). Therefore:
- Single Turret: (3*1+12)/1 = 15 combat rounds endurance before needing external reloading
- Dual Turret: (3*2+12)/2 = 9 combat rounds endurance before needing external reloading
- Triple Turret: (3*3+12)/3 = 7 combat rounds endurance before needing external reloading
Extend that basic accounting to include lasers as well and you've got an upper limit on the duration/endurance of space combats, absent additional reserve tonnage dedicated to weaponry.
Additionally, such a combat endurance understanding provides "a reason for different types of turret to exist" other than just being "cheap" on purchasing the turret itself.
- Single Turret: reduced firepower per combat round, longer endurance
- Dual Turret: balanced
- Triple Turret: increased firepower per combat round, shorter endurance
In circumstances where "longer endurance can win battles" ... opting for single turrets rather than dual/triple turrets can make a lot of sense, depending on threats and use cases.