Lazy Daze Owners' Group

My method of flushing has worked well for decades, it uses the natural flow and pressure of the transmission fluid as found inside an idling transmission, nothing unusual happens to cause issues

When setting up maintenance schedules, I use the Factory recommendations,  The Factory knows your vehicle better than anyone else, having spend years and hundreds of millions developing and testing it.

In the previous life as a Mechanical Repair Supervisor at LAX, I had to set up maintenance schdules for hundreds of pieces of equipment and vehicles, so the computer system would issue work orders at the proper time. The Airport's fueling system recorded the mileage each time it a machine was refueled, helping to enable the timely manintenance.
In two decades of doing this, I relied on the maintenance manuals that came with each machine, plus whatever trends we noticed reviewing the past records on similar machines, we did a some preempltive repairs and maintenance based upon our own experience, every operating environment is different.
Much of the equipment we maintained was considered to be mission critical, the maintenance and test runs needed to be up to date, building emmergency generators are a good example of machines that need to always run, when needed.
 
When it came to oil, we used oil analysis over several years to verify the change intervals, the best way of determining how long oil will last in regular and HD usage. Over several years, it was determined that regular engine oil was good for 7000 miles and synthetics for about 10,000 miles in cars and light trucks. We exclusively used dyno oils unless a machine’s manual required synthetic. We decided on a 7000 mile interval, 10,000 miles was considered too long to go without a through inspection, normally done when the oil was changed
Transmission fluid and axle fluid changes were left at the Factory recommendations.
Brake fluid changes were set at three years, due to moisure build-up..

The power steering and power brake hydraulic fluid does not have a listed change interval. I flush and change our LD’s power steering fluid every 50,000 miles and have added an inline filter on brake booster’s return line, it too gets changed at 50,000 miles
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I have done this on every power steering equipped car have we have owned  and have never changed a steeering box or power steering pump. We tend to keep vehicles a minimum of ten years, usually much longer.

1999 to 2007 LDs are equipped with a transmission mounted parking brake, it contained a few ounces of the same fluid used in the transmission. The parking brake can develop leaks and seeps, it’s fluid leve needs to be checked regularly and topped off.
Failure to do so could lead to its failure, a $1500-2000 repair, and in some cases, when it seizes, it tears off the rear of the transmission, now you are looking at a hugely expensive repair. Check the fluid level.
Parking brake oil fill | Flickr

Ford has taken care of deciding the schedule you should use, based on normal or heavy-duty use. They determined the schedules based on millions of test miles plus feedback from existing fleet owners.  
If you want to change any of the fluids more often, go ahead but do not expect a much longer life.

Larry

…and take the used atf to AutoZone for recycling.