What is the maximum cruising RPM speed that my car can handle for long hours of driving?

My car is a 2003 Honda Element with 4wd and a 4 speed automatic. The maximum RPM speed(before redline) is 6,500 rpms.

The car when brand new has 160 hp and 161 ft lbs of torque. Currently it has close to 129,000 miles on it.

My question, how fast can my Honda cruise at COMFORTABLY and at the same time still last up to 3000,000-400,000 miles(well it's a Honda).

From my experience, Honda engines are designed to rev and sustain higher rpms but I only heard that with VTEC engines. My Honda has an IVTEC engine.

How to get 12v from a 6v power source?

I have a 1982 Honda C70 Passport, it has a 12v battery. I changed all the blinker lights and the brake light to 12v led lights. The head light on the other hand is a 6v 25w light and runs directly from the power created by the engines stator. I was wondering if it's possible to boost the 6v to 12v? I also have looked for 6v 25w led headlight bulbs, but it seems 6v are in the past and I can't seem to find any for sale. The only option I see is upgrading the engine or hooking the headlight to the battery power, but I fear this will kill my battery faster and this isn't how the manufacture intended it. Any ideas as to get the 12v led working from a 6v power source?

Which sport ATV should I get?

I'm not sure in what to buy a honda trx400ex or a suzuki z400, or a raptor 660r the thing is, the zusuki and the raptor are the same price, the suzuki looks really clean, i mean the three atvs look great, but i just want them to go to a mountain environment. The honda is cheaper, but i'm afraid that it doesn't have the power to climb or overheat (air cool engine) the suzuki and the raptor are liquid cool. I have heard that the raptor 660 is problematic (engine issues) while the suzuki and honda are bullet proof machines. Need some advice. Sorry for my writing.