Tell me if I am wrong, those strips test for moisture only in the fluid.
The fluid that is down by the brakes does not get a chance to mix well with the fluid up in the reservoir.
Its well worth just bleeding $5 worth of fluid through once every year or 2.
Fluid in the calipers is subject to very high temps & will in time decompose. The inhibitors/additives will also be depleted in time in the calipers because of the heat.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving