Brake bleeding necessary?

I was wondering how necessary brake bleeding is. I realize that too many bubbles in the line can cause a large problem. I am asking because I will be changing the brakes on my sister-in-law's car, and want to make sure I don't subject her to any dangerous situations.
I have changed the brakes on my own auto before, and whenever I have done so, I have made sure to leave the master uncapped and completely full of fluid. I have never had any problems with my brakes after doing such.
So, basically, is bleeding the brakes necessary if proper caution in maintaining fluid levels is excercised?
I ask as well because I am not sure I will have an assistant, therefore, the bleeding is almost impossible.

Thank you for your time

I was wondering how necessary brake bleeding is. I realize that too many bubbles in the line can cause a large problem. I am asking because I will be changing the brakes on my sister-in-law's car, and want to make sure I don't subject her to any dangerous situations.
I have changed the brakes on my own auto before, and whenever I have done so, I have made sure to leave the master uncapped and completely full of fluid. I have never had any problems with my brakes after doing such.
So, basically, is bleeding the brakes necessary if proper caution in maintaining fluid levels is excercised?
I ask as well because I am not sure I will have an assistant, therefore, the bleeding is almost impossible.

Thank you for your time

When you say "changing brakes", do you mean changing brake pads?

If so then yes that can be done without bleeding the brakes (but it is often a good time to bleed the brakes and change the fluid).

I am referring to changing the pads and rotors on the front. I may not have access to an assistant, which is why I am wondering if I can get away with out doing it. How much extra work is involved in changing the fluid?

As long as you dont open the system you dont have to bleed it. By open I mean unhook any lines, which you dont have to do to change the pads.

Leaving the MC cap off for any length of time should be avoided. The brake fluid can draw moisture out of the air. Flushing the lines is a good idea if the fluid is around 3-5 years old..

What I do every time I change pads which would be about 2000 times and counting. The dirtiest fluid in any brake system is found in the calipers because that is where fluid is subjected the greatest heat. The worst thing that can be done is pushing that contaminated fluid through anti-lock valving and back into the master cylinder. Open the bleader screw and squirt the dirty fluid into a cantainer for disposal as you push the caliper piston(s) back into the caliper bore. Close the bleeder screw with the piston compressed. Put that caliper back onto the bracket, and open the bleeder screw again. You will observe a few bubbles being pushed out by gravity flow. Don't let the M/C resevoir get completely empty, yet the less dirty fluid remaining before refilling the better. Then go to the next brake you are replacing and do the same. This works very well on disc brakes because they do not have a residual check valve, the bleeder port is by design at the very top when the caliper is set in place. Take a look at the fluid that you have removed. Who would add that dirty fluid to a brake system resevoir? When you refill the resevoir with clean fluid it won't really matter if the cap was removed. You will have new fluid in the system and no air bubbles.

most people don't ever flush their brake fluid. For this reason, I usually recommend flushing the system whenever brakes are needed, because chances are, it'll be the first on its ever had.

You may believe that its not a very necessary maintenance item, but a very high percentage of failed brake components are due to this very issue....which is very cheap and easy to do.

There is no reason to "blead" the system for a regular brake job.....although many recommend that you open the calipers when you callapse the pistons, to prevent the fluid from back feading through the ABS module and master cylider, possibly forcing floating material that was in the calipers into sensitive components......but either way, if you flush the system, its mute.

At the college we're anal about flushing, so it's become an every brake change thing for me.. Water=corrosion=ABS/caliper problems..