How long can I use a car battery without charging?

I have just bought a multimedia screen for my 2000 Honda Accord. How long will I be able to watch movies on this without the engine running? I was thinking about installing a Voltmeter in my car. Will this be beneficial?

About a month ago while i was driving my Honda Accord 1999 EX V6, the car shut down?

Radio shut off, lights went dim, then the engine shut off right as i got in my driveway. I tried starting it again but i kept getting a ticking sound. I was told it was the battery so i went and got a new one. Got the battery and my car is running fine for about a week. This time when it died it was making a different sound. Instead of it making a ticking sound, it sounded like the engine was trying to turn on like "r-r-r-r-r" but it wouldn't turn over. During both of these incidents all of my dashboard lights would turn right before it dies. The battery light, fluid, doors would show that they are open, brake light, and check engine light all would be on before the car shut off. Now i was told it was the alternator. I went and got a new alternator put in and it was working fine for a few days then the 2nd issue started to reoccur. Sometimes the car would start but if i started driving it before it was all the way heated up, it would shut off. I ended up getting a tune up hoping this would do the trick. Got new distribution wires, distributer cap, roter in distributer, and 6 new spark plugs. Car was working when i got it back from my mechanic. The next day, the same problems occurred. I took it to AutoZone where they told me that it could be the MAP sensor that it causing it to fault. I went and fixed that, and the car was working until the next morning when i went to warm it up. Same issue, it shut off at a certain temperature. Now i turn the key and get absolutely nothing.

Added (1). Honda Accord 1999 EX V6 does absolutely nothing when I try to start the car, what could it be?

Honda Accord 2.2 Dtec clutch?

I have ta 2009 honda accord 2.2 dtec engine manual. It have 98k miles rights now. The clutch pedal is making a squeaky noise when releasing it slowly and lately its doing it more often. My mechanic put some silicone spray but id did work, also when i'm shifting the gears are not that soft like they used to be. Do i need to change clutch kit? What does the clutch kit do exactly? Found one with a good price and thought maybe i replace it. I'm asking cause i'm don't know much about mechanical.

I think my car burning gas too fast? - 1

I have a 2003 Honda Accord(sedan) V6 3.0 liter engine with 140,000and I'm only getting around 260 miles on a full tank, shouldn't I get more?

Any suggestions?