I replace my front brakes and my brake calper do.

Yes, bleed the entire system.

Roy

I do it only if the brake pedal/stopping does not feel right.

If you had a good brake pedal before you replaced the brakes and you didn't open any brkae fluid lines, then you don't have to bleed them at all. However, once you finish the brake job start the engine and press the brakes 10-20 times to push the caliper piston outward to it's proper position. The brake pedal will go further than usual toward the floor until the pistons are in the proper place.

So do your brakes work ok? Or are you just gonna bleed them to be SAFE as they say? If you are gonna bleed the back, then yah, it's easier to replace the cylinder to do it. Although I have drilled out old screw, retapped, used my thumb to bleed, and then reefed in a bolt to seal it in emergency situation.

U will need to replace the wheel cylinder they are cheap enough.

You can also bleed form wheel cylinder itself by taking a shoe off and letting cylinder piston leak the air/fluid by using hand to restrain pop out and then re assemble.

You will need to replace the wheel cylinder. Another cause for a low brake pedal is that the rear brakes are adjusted properly. This will cause a low brake petal also.

I personally hate workin on brakes on older cars since the parts are usually rusted up. Lots of hassles to deal with if your not careful. Replacing parts is easiest route but also can dent the wallet.

Is the wheel cylinde leaking?
You can bleed from the fluid line where it goes into the wheel cylinder.