PWM duty cycle in a solar charge controller

I run a Morningstar Tristar PWM 45 solar charge controller that is fed by two 140 watt 12 V nominal panels (Cynergy) mounted fixed and flat. Batteries are currently 2 x 6 V GC from Costco. I run a custom charging profile and the Tristar uses a % duty cycle threshold and a timer for the absorption to float transition. I've changed those parameters many times and have long since forgotten what the original default % duty cycle threshold and timer setters were. Right now the settings is to change from absorption to float when duty cycle is 25% or lower for 5 minutes. I know the basics on what the duty cycle is, it is the percent of time that the controller allows solar current pass through from panels to batteries. But can anyone please educate me on the proper use of these parameters?

Should the duty cycle threshold be adjusted based on max potential solar input? For example, during winter storage I will never see the same max potential solar amp input (~15 amps) that I can get during summer due to low sun angle. 3 amps is more like the max that I expect to see. Does that make a difference in what the % duty cycle and timer settings should be?

Another example, during winter when things aren't being used I use a 14.8V setpoint for bulk/absorption charging with temperature correction. But for camping season I have to drop that voltage setpoint down in order to use my larger inverter because otherwise it faults out on high input voltage. That's a whole other discussion, but my remedy has been to drop my bulk/absorption setpoint to 14.5 V and turn off temp correction in the cold adjustment direction. Should I change the % duty cycle and timer parameters in the charging program to accommodate better charging at this lower voltage?

Thanks.