Horn ground

Since I just opened this not too long ago ill ask real quick to see . How long do yalls batteries last before you have to charge them ? Given i was messing with signals and horn my battery is bout dead again . I had filled it with distilled and charged it for hours till it was good to go . Guess what Im asking is if it is normal to have to charge a battery once every week or two .

How often do you ride her?
More you ride, better charged she'll stay, as long as your charging system is working right.
Charging every week or two is too often.
Battery sounds weak, or it's dying.

When I'm riding, maybe 4 to 8 times a month, I'll need to give the battery a charge every second month.

Since motorcycles have direct drive alternator/generator they don't charge unless running at speed. If running around town at slow speed, battery may not get enough charge to last long. If doing work on bike with ignition on and not running then not charging. Remember long rides are good for bike and the bike rider.
When working on bike electrical, I use an old car battery jumped to the bike. It last a long time between charges and does not weaken bike battery.

What voltages due you have at battery when off, when idle, when rev engine to 2,500 rpm?

It is grounded through the switch which is then grounded to the handlebars. The black handlebars are painted so your switch will not ground like it would witht he stock chrome ones. I too like running the black handlebars and found there are two ways to get around this.
1. sand the black paint off where the switch grounds at.
2. My favorite, run a grounding wire from the switch to the common ground on the frame. I never liked relying on the contact between the switch and handlebars for my ground.
Your battery should never need charging unless you let the bike sit for long periods of time or you are doing trouble shooting and using the battery as a power supply. If you are constantly having to charge the battery under normal use there is something wrong.