If there is a good reason to have any or all lights on, then use what you need. If in doubt, turn them on - unless you're going to blind someone else. Note that most planes equipped with strobes are placarded to turn them off in cloud.
However....
If you own the plane, or would like to be kind to the person who does, don't use lights, particularly landing lights without good reason. Letting alone the comparitively small cost of the bulbs themselves, there is a much more expensive hidden cost in alternator drives.
Assume that the alternator is carrying all of that electrical load. Let's roughly sum it up for a Cessna 12 volt circult: Beacon 7 amps, 3 nav lights, 5.6 amps, strobes 3 amps, landing light 20 amps = 35.6 amps, plus the 1.8 amps of the basic airplane, plus 4 amps for radios, plus maybe you're cautious, and have the pitot heat on 6.5 amps = 47.9 amps. We won't get into the 15 amp flap motor right now...
So you're thinking 60 amp alternator, so no problem carrying that load, and indeed it will, but that is 575 watts, or 3/4 of a HP. Still no problem... but HP is speed (engine RPM) times torque. The alterntor is designed to operate at the torque through it's normal operating RPM, but not at idle, while gliding in to final approach, with everything on. RPM half = torque doubled. If your alternator is belt drive, that's not so bad, you're just working the belt really hard.
However, some Continentals have gear driven alternators, These all contain a flexible drive coupling. That coupling, particularly on 520/550 front mount alternator engines, is an expensive consumable, and it's failure can lead to other even more expensive damage, when it fills the oil system with bits of shredded rubber.
So for the sake of the alternator drive, use less electricity whenever you can. Personally, when I'm landing my 150 at night, I turn off the alternator when I turn final, and use only the battery for the minute or two of the final approach. Back on when I taxi off, and I let the engine coll down a bit above idle, with the lights off, and just monitor the ammeter to see that it is topping off the battery.
It all sounds anal, I know, but I was employed for two months to try to design an improved alternator drive coupling for the 520/550, and could not do better than what was out there, which is only moderately good.
If you need to, light up like a christmas tree, but if you can conserve some electricity, you might be saving more maintenance expence than you thought!