While golds, ambers and browns may be acceptable fall colors, they aren't what you want to see when inspecting blinds or shades for cleaning. If you ignore the effects of UV and aging on plastics, it will be to your own peril. Who wants to have shades falling apart as they hang on the drying rack or in the window? How about broken clips that make it impossible to rehang the shades again, until they are replaced - if you have suitable replacements?
As the typical window treatment is exposed to plenty of sunshine and hangs for a period of time, the plastic or vinyl parts that are present will age and become brittle. Some of these materials will go from a clear to amber to brown as they get "sun burned" with age, and become very brittle. The new vertical channel panel (groover), that may be bent into a loop and spring back flat when new, will explosively scatter shards all over the room - if you tried the same trick when the sides of the channels are brown. Some clear or white plastic parts, in the header of faux wood blinds for instance, may not change color. However, they will crumble under stress. Hanging in the window they may appear just fine, but when taken down, handled and cleaned, will they still be fine or will pieces break on anchor tape drums or will bottom rail buttons pop off or crumble?
Over time, many plastic products loose some of their elasticity and flexibility as their molecular composition changes slightly from exposure to ultraviolet light, environmental factors and simple aging. While it is easier to detect this change when the plastic leaves visible warnings, it may also be easily overlooked when it is invisible or more subtle. Asking the client, "How old are your blinds?" is certainly a question that aught to be an ingrained part of your conversation in any pre-inspection before cleaning or repair quotes are discussed. You won't always read or find a production label or date, so take their answer under advisement as "time flies" and the treatments are often a "few" years older than they may believe them to be.
Having been forwarned by their answer or the colors you see, you can then address any concerns about possible degredation of the plastics with the owner. Pay particular attention to the sunny side of the vane, and the bottom edges as broken or cracked edges may be present - which they hadn't even noticed. Sun burn spots or discolorations on slats can not be removed with cleaning. While vertical channel panels that are light yellow may still be cleaned with careful handling, at some point you take a risk of damage as the color or their age increases. Dark amber or brown discolorations are signs that recommending replacements may be a better choice than cleaning. Don't forget when dealing with verticals that the vane clips also may be brittle and may break if you are flexing them, or removing and replacing vanes for cleaning.
Careful pre-inspection and taking the time to insure the client understands the aging process could become a factor with cleaning. The water from the cleaning or the soaps don't cause the plastics to break, age, or stress, but their existing condition may. Don’t assume liability for cleaning these amber oldies unless you like buying new channel panels or repairing parts in headers, instead of selling new blinds to the client. Don’t allow their problem to become yours.
Offering clients the option of replacing yellowed valance channels on mini blinds with new ones, or simply removing the panels makes sense in many cases. Brittle valance clips are just a part of life for a professional blind cleaner. Stocking an ample supply of the most common clips is advisable. Also, incorporate into your pricing the cost of these parts, or have the client pay for them as needed, if that works better for you. Using velcro tabs or buttons are a practical alternative in some instances or in emergencies.