Wool lends itself to easy “spot cleaning” without washing the whole item. In the old days, wool suits received little sponge baths (focused on soiled areas) in between full-scale cleanings. Women would also get their tea pots boiling furiously and aim the steam at the fabric. (Remember to take care: A burn from steam is worse than one from hot water. )
According to Permanent Style of London,
Dry cleaning twice a year should be sufficient for a suit worn once or twice a week. … To lengthen the life of your wool suits, put off as long as you can taking them to the dry cleaners where harsh chemical are used in cleaning.
Black Lapel advises:
[T]here’s nothing that will beat up your suit jacket and wear it out faster than frequently taking it to the dry cleaners. While a trip to the cleaners every once in a while is inevitable, do so only when visible dirt or odor has built up and spot clean the dirty areas rather than have them clean the entire suit jacket. Dry cleaning will expose your suit to harsh chemicals that will eventually take its toll on the fabric.
Instead, use a modern steamer designed for home use! While they can be rather pricey, I have seen them at discount stores for under $100 or look for one second hand. Also, brush your wool suit after you wear it as that will remove particles of dirt before they get ground into the fabric. (Remember those old movies where we saw valets brushing suits? Check out Jane Austen’s World to read about the life of a valet.)
Now, Black Lapel is writing for a male audience, but what he writes can be safely applied to women’s wool suits, skirts, slacks and dresses. In fact, as women’s suits tend to have less internal “structure” (what Black Lapel calls “internal canvassing”), suit jackets might be a little easier to steam clean.
Wearing your woolen sweaters over a shirt (on that will absorb odors and moisture) will also help increase the number of times you wear your sweater before you want to wash it. A woman would be well advised to wear a thin t-shirt under the blouse and thin leggings under her winter suit; wearing two layers will help keep your wool jacket clean.
Remember, if the wool has not been treated to machine washable, it is better able to repel dirt, odor and sweat. You will be able to wear it more a single time.