Wool sweaters do not need to be washed particularly often. Instead, hang the garment out for airing occasionally and it will soon revive and feel clean and fresh again. When you wash, look for washing instructions in the side seam. Most of our wool garments can be washed in the washing machine, using the 30oC (approx. 80oF) wool program. When washing by hand, rub gently to avoid felting.
Not only will your wool garment last longer and look nicer if you treat it like above, you will also save the environment by airing it instead of washing it.