Moth damage occurs to vintage wool blankets typically when they are not being used or are in some sort of storage space. Clothes moths will usually find darker, quiet places that do not get much activity or human traffic and place their eggs there.
If they find your vintage wool blankets in a location like this the wool larvae will feed on the wool blankets and this is actually what causes the damage, not the clothes moths themselves.
To prevent this you use airtight storage bags to store the wool blanekts when you are not using them for long periods of time. If you put your vintage wool blankets up for just a little bit at time you most likely will not get any sort of moth damage, but just to be safe make sure that they are completely cleaned and brushed.
If you leave any sort of wetness or dampness on your wool blanket while storing it the chances it will get moth damage will increase greatly.
There are some chemical soltutions for protecting your wool blankets which you can also use. Things such as moth balls, will also work.
You can get some moth repellent spray and cover the wool blankets but you will usually want to do this if you are going to be storing them for an extended amount of time, not if you use them daily or weekly.
If you do believe that moths have laid larvae eggs on your wool blanket you can brush them clean or for best results take them to a dry cleaner.