I try for 1000-1500 AGL for shorter trips. Lower and my noise print is more than I want, higher and it takes me more than 45 sec to get down on the ground in the event of an urgency. But crossing the English Channel, 5000 to give me more chance in the event of engine failure (never happened yet, touch wood).
Longer trips, and jet turbine gives an optimum altitude of 4,500-5,000 AMSL
But then, that's a helicopter for you