Which laptop should I ask for for graduation?

I just graduated from high school, and I want my first laptop for college. No more than around $900. Here are some that I'm looking at. I wanted to buy a customized HP Envy, but it doesn't have that battery life I'm looking for, but is still an option for sure. A MacBook Air, ew I know, but they last FOREVER and have GREAT battery life. Or a Lenovo or Asus of some sort. I want an Envy because it's powerful, and has awesome Beats Audio. I would want a MacBook Air because of the battery and longevity. Also a THinkpad or Asus because they are also so durable. What do you think? Oh and my parents said they'll put $500 towards a laptop.

I like the way you think -- being a college student and living student life demands your laptop to have long battery life and being durable. Think of your specialty -- if it will have anything to do with design and\or engineering you need a 17" full HD display.
In fact, you need as much resolution as possible on any screen -- it definitely worth investing money.
Don't waste your money (and laptop weight) for dvd-drive -- it's an absolutely useless device in the world of usb 3.0, flash, and external drive.
Heading for a good sound is laptop might not be wise -- laptop PHYSICALLY isn't able to produce any decent sound, any $30 Chinese stereo system will do better.

Another thing is memory - 6 Gb is ok, 8's better.

if you are not in design, 3d or video editing, there's really no need to run after any super-cool processor, all the modern models have enough productivity for any everyday usage.

1) Can the hard drive be removed and replaced with something bigger or faster? (or working should the drive die).

2) Can the memory be removed and upgraded?

3) Can a larger battery be attached?

My wife's Mac Book (2007?) hard drive died and it was one of the last time of Mac Books that actually let you swap out the old dead drive. She had the original restore CD, so I spent $99 on a 128gb SSD drive (much better than the original drive), slapped that in ran the restore CD.

If this was 2011 Mac Book, it would have cost me far more than $99 to replace the drive because the hard drive is more or embedded into the device and I end up spending a few weeks shipping it to Apple to fix, paying for labor and parts. Mind you the labor was something I was able to do on my own, remove dead drive, insert new drive, run restore disc, its not that complicated.

Sometime fixes for broken components can be really easy to resolve, but not if you can't remove that component, not if its embedded into the case.