Well you are right & your are wrong.
Firstly unless you have fitted new field windings & armatures your old 3L's will not be putting out their stated 80 Watts to start with probably closer to 40 to 60 Watts.
Then yo can start looking at all of the old switches with weak springs and arc burn on the contacts followed by grubby oxadized bullets usually with less than 1/2 of the original wires still intact.
It is always fun to measure the voltage at the globe contacts on the bikes of people rubbishing Lucas electrics.
IT is generally around the 3-4 V mark, thus you have to be running fast enough to be producing the full 7.5V in order to get something better than 5 at the globe.
Ask riders when was the last time they cleaned ALL of the contacts on their regulators & most could not even tell you where they are .
Way back in 1956 there was a 4 page spread in The Motorcycle "Are you running Negelectrics ?".
We used to reprint it in The Banter from time to time, when bad lights happened to be topical.
At the ABR's people would ask me what I had done to make my headlight so good, what secret globe / genny/ regulator was I running.
The answer was a rewire with new blade connectors and replating the reflector.
Put most bikes on the stand, and give then a fistfull with the lights on and just about every headlamp will flicker because the switches are worn out, particularly the dip switch if fitted. solution is new switches or as I am prone to do relays , particularly the double pole double throw for switching beams so you are never left in the dark unless an element blows. ( you can even use a 2nd relay to switch the lights on & off.
Some times making things more complicated actually does make them better.
I too got bitten by the LED bug but in my case it was because my globes are no longer being made and the remaining stock are all past their use by dates so when given a good shake, the cement fails and the glass drops off into the reflector or the elements simply burn up.
Thus I was forced to go either for high pressure halogens or LEDs.
The lower power consumption of LED's reeled me in hook line & sinker but I am yet to find one that throws more useable light than the std 25/25 tungsten globe.
Same as Julian, the wallet was fed up with buying very expensive globes that just did not throw sufficient light to ride by.
Excellent light to read a map by but just not enough to be able to see the road at much more than a brisk walking pace.
As Black Sheep noted, the new stop / tail globes are brilliant and I now use one that throws a very strong pencil beam of light back that you can see for miles.
So much better than the "bulbs that last 4 ever " circuit board fitted to the A65 which had very poor beam spread from the 5 deg LED's used on the board.
OTOH it is still there & still works although I have not ridden the A65 for quite some time.
The best light I even had from a 6V system was to toss the Lucas reflector & fit a VW Kombi one then use the 6V halogen VW aftermarket globe.
This was fitted to the B40 , gave excellent light and ran for decades without any problems.
As for the blind farts who can not see unless they are throwing 10,000,000 lumens of miss aligned light illuminating everything in a 5 mile radius from either side of their of their wanker waggons, yes they are a nuisense.
I have 2 std practices to overcome them if they are behind
1) go down through the gears till the bike is at a crawl till they pass
2) swerve abruptly onto the verge till they are gone .
Some times they even stop to offer assistance which when time permits allows me to explain how they are making it very dangerous for other road users with their excessive light and on a couple of time the villian has agreed to sit on my bike with my lights on while their partner turns their bitumen melting appartus on & off.
Usually they appologise as they had no idea just how strong the shadow of their lights was.
As for cars coming the other way all you can do is use the "night eye" trick.
As they approach , close one eye and watch your verge .
Once they have gone past switch eyes, give the blinded eye 30 seconds or so to recover then reopen it.
If you still see a red ring, close it again.