Flush Brake Fluids and Power Steering Fluids Economically

Mineral and vegetable oil brake fluids became obsolete many years ago apart from a very few exceptions and these were replaced by a universal glycol based type which is virtually the only type available from the majority of retailers.

Early glycol fluids had a relatively low boiling point and have been replaced by types with higher boiling points so currently there is generally two types available - in Europe these are DOT 4 and Dot 5.
DOT 4 is suitable for all clutch and brake systems (apart from a few exceptions) of low and medium performance vehicles and DOT 5 for the braking systems of high performance vehicles. Most people most of the time find DOT 4 a better all-round fluid and because the information surrounding DOT 5 (and 5.1) tends to be vague and suggests at least some are silicone based which can be harmful to some hydraulic seals.

The main problem with glycol based fluids is many braking hydraulic systems are vented to atmosphere and the fluid is hygroscopic and absorbs atmospheric moisture which lowers the boiling point. This is why a brake fluid change is part of the modern service and maintenance schedule.

Surely your not waiting for 90,000 miles
to do all sorts of things
By then you should have changed your transmission
& power steering fluids at least 2 times & flushed your
brake fluid every 2 years on all vehicles
I do Air,Cabin,Fuel Filter & Spark Plugs every 3 year
What your asking is Manufacture Recommended Service
Wait on that you will either break down or have a vehicle
that won't last much past 100,000
The question you ask is in your owners manual
You need a vehicle Log Book
You need to develop your own Preventative
Maintenance Schedule based on time as well
as mileage & forget the manufacturescheduled
maintenance,your schedule will include theirs
& much most based on your lifetime of knowledge
& experience & repairs
You treat ALL Vehicles the same
It's not a wait & see game
It is about education & preventing problem
down the road
No vehicle manufacture really care what you do
or they would tell you about power steering,brake
fluid & stop with the silly 100,000 spark plug & trans
fluid changed,by then the damage will be done

From Owner's Link:

Maintenance Minder B Scheduled Maintenance
Recommended service for your 2006 Honda Ridgeline:

Replace engine oil and oil filter
Rotate tires
Inspect front and rear brakes
Check parking brake adjustment
Inspect tie rod ends, steering gear box, and boots
Inspect suspension components
Inspect driveshaft boots
Inspect brake hoses and lines (including ABS)
Inspect all fluid levels and condition of fluids
Inspect exhaust system#
Inspect fuel lines and connections#

Adjust the valves during services A, B, 1, 2, or 3 if they are noisy.

Maintenance Minder 6 Scheduled Maintenance
Recommended service for your 2006 Honda Ridgeline:

Replace VTM-4 rear differential fluid: Driving in mountainous areas at very low vehicle speeds or trailer towing results in higher level of mechanical (shear) stress to fluid or frequently fully loaded. This requires differential fluid changes more frequently than recommended by the Maintenance Minder. If you regularly drive your vehicle under these conditions, have the differential fluid changed at 7,500 miles (12,000 km), then every 15,000 miles (24,000 km).

Most of that is not scheduled maintenance items. I would have your fuel filter replaced, if not done yet, it should be done every 20,000 miles. Alot of these places get a small commission for selling added services. I would go by the maintenance schedule in your owners manual.

If you live in an area of frequent high humidity, it might be a good idea to do it as a preventative measure since both brake and power steering fluids are hygroscopic and could absorb enough water to affect their performance. Since most hydraulic fluids also suffer from exposure to heat over time, that might also weigh in the decision.
I probably would not personally opt for it since your mileage and the age of your car don't seem to justify it. These things always seem like the medical equivalent of tonsillectomies; a (related) doctor once told me that those were often not necessary and could be treated with medication unless chronic, but they were safe surgeries and helped pay the rent.  
I do recall being told by an automatic transmission specialist that unless something failed, don't do anything to it. He said the changing and flushing could introduce contamination that otherwise wouldn't be there.