661KTAS
Am not an authority on Lycoming engines (except the IGSO540 series, superb...IMO), but new engines/cylinders should be run very hard for the first 10 to 15 hours (max BMEP) to ensure longer life.
OTOH, if you look back many years to the piston engine airliner days, these engines were routinely cruised at 45-50% of rated power, for longer life.
If your flights are for sightseeing (endurance, 30 minutes, one hour, etc), a lower cruise power setting will result in lower fuel burn.
Conversely, if the idea is to cover as many miles in the allotted time, then higher power settings will be appropriate.
The key to longer engine life is for it to be operated every day, whatever the power.
Hope this has been helpful.