Should be done at least every two years. More often if you live in how humid areas because brake absorbs moisture. You can do it yourself with gravity one wheel at a time or all four and the LSPV. I have tubing that works on the bleeders so I do all four at one time (I do not have an LSPV). I buy a quart of fluid, get four containers and pour about one inch of fluid into the containers. Top off the MC. Set the container on the floor, push the tubing on to the bleeder nipple and stick into the containers. Start opening the bleeders in the same order you bleed the brakes DR, PR, PF, DF. Check the MC often and do not let it run dry. When the fluid starts running clear in the same order tighten up the bleeder. I then just pour the used fluid into the container that I put the used oil in for recycle. If you do this often, you will never have any problems with the system. What happens is the moisture settles to the bottom and corrodes and pits the MC, Calipers, and wheel cylinders. Takes about one-half hour to do it.

Another thing if you have a container of fluid that has been opened for more then a year you should recycle it. Do I do it as flush as often as I should, NO!!!!!!!! Do I throw out fluid that is over a year old, NO!!!!!!!!!! But I should!!!!!!!!