1846 - 1853
State militia groups, by and large, followed the equipment guidelines of the US Regular Army, and we do have the record of the Washington Artillery having carried white wool blankets into the Civil War. If they did follow the US Army's lead in this area, we know that in the era of the War of 1812, the US Army issued their troops a white wool blanket that had blue end stripes. For the 1820s era, the US Army issued its soldiers a white wool blanket with blue end stripes - and the letters "US" stenciled on it, literally marking it as a government-issue item. For the Mexican War era, the US Army issued its soldiers a white wool blanket with blue end stripes, and with the letters "US" stenciled on it. So we have reasonable cause to think that the Washington Artillery did have white wool blankets- and likely with blue end stripes - from their beginning as a state militia unit.
As we know, the Washington Artillery was a state militia unit from 1838 forward. As we also know, they were renowned for their excellence in both Infantry and Artillery drill, but were not particularly known for their habit of self-deprivation. When they bivouacked for field training and a marksmanship competition with other militia units on at least one occasion, they suffered the hardships of occupying one floor of a hotel in Pass Christian, Mississippi. It would seem unlikely that their wool blankets would have suffered too terribly much from anything except moths, then, and we suspect that the blankets issued them at any point before the Civil War would probably have had a pretty high survival rate, if field use was the great destroyer of blankets.