Having more than one aircraft departing to the same destination at the same time is only going to take demand from an hour either side of departure time. Optimum timing is 2 hours separation, 90 mins is OK. The total demand for the route is spread over the day, some pax want to get out to a business meet or holiday, others want to get home later that day. That's the business you're fighting for.
Departures times to leave less than an hour before yours will certainly affect your LF's. Try to tweak your schedules to depart 90 mins before the competition on that route if you don't want to get into a scheduling war.