Voltage usage on the stock Triumph.
Dim Headlamp: 40 watts
Instruments: 5 watts each (most have two so us 10 watts)
Tail light: 21 Watts
Warning/Bright/Blinker lights: 2 watts
Coils: 10 Watts (times two if you have two Coils)
Electronics: 18 watts (from what I can surmise)
If you run the stock headlight all the time you use up a significant portion of the power produced! The law of diminishing returns comes into play. The more power (watts) you use, the faster the battery drains. You have to run the bike for a long enough period of time with a reduced load to over come the period of times that you ran with the large load. That is why Motorcycle lights were only ran at night! And thus the legend was born LUCAS, Prince of Darkness. Also, the famous quote by Joseph Lucas : "A gentleman does not motor about after dark." was born.
So you invest in a good battery. This will help! But no, it just delays the Unenviable. The battery drains slowly, down, until it too low to run the ignition or you turn on the headlight and the bike stalls (low voltage when the light sucks up the power)!
OK, now install a bright headlight so you can see what you are going to hit! More watt usage! This just drains the battery faster.
So charge that battery every once in a while depending on your usage or bite the bullet and get a higher Watt stator. Stators come in 200, 220, 210 and several other watt output.
You can also reduce the electrical load on the Bike, charging system, and the Battery by using LEDs. The article "Help 114: LEDs" outlines the reduced watt consumption experienced when LEDs are used. The LEDs article is in the "Past Mike the Motorhead Issues:" on the "Mike the Motorhead Page".