How frequent do you need to change....

[jb92563]

I did mine in under 30 minutes @ ~5min per wheel.

Here is the video. brake flush - YouTube

There are 2 nipples to bleed but the video only showed me doing 1 I think.

You want to alternate between the gold and blue brake fluids on alternate changes so you can see in the tube when the new colored fluid starts and then let it flow for a couple seconds longer for good measure.

I also bought a pressure bleeder and it paid for itself immediately.

I cringe to imagine what a shop would charge, when you could train a monkey to do this very easy DIY task.