The use of landing lights would make a difference as follows:
(a) On departure and arrival while below 1500ft (including circiuts)
(b) When advised of or aware of conflicting traffic
(c) When transiting 'choke points', en-route VORs, VRPs
(d) In areas where miltary traffic is operating
(e) In poor visibility or wx
I have always been under impression that there is a culture of avoiding the use of landing lights within UK flying schools, which is down to the cost of replacement landing light bulbs.
However, I was once told by an engineer that landing lights had a long life while they are being cooled by an airflow, perhaps someone can clarify this.