Hard to give a definite answer without more data and turboprop operating manuals contain quite sparse info.
In most medium/heavy jets this issue is addressed by using cost index - if properly calculated it enables to establish a speed schedule, which will yield the lowest total cost, taking into account both fuel- and time-related costs.
It definitely does not make sense to fly max speed, as the fuel cost will skyrocket, nor does it make sense to fly too slowly.
There surely is some optimum speed to fly, but as I remember from my turboprop days - nobody knew what it was
Having said that, turboprops burn quite little fuel compared to heavier jets, so probably slowing down does not provide significant savings. Extending time OTOH could influence maintenance cost.
My guess is that’s why nobody bothers to use cost index and t-props manuals normally only contains performance data calculated with MAX CRZ PWR.