Always store the sleeping bag in a cool, dry place by hanging it up loosely or inside a larger storage sack (for example, an old duvet cover). Do not store it compressed in a stuff sack or under damp conditions as this will damage the insulation.
Away from home
It’s a good idea to turn your sleeping bag inside out and allow it to lie open and dry while you’re having breakfast or packing up the tent. Because: a certain amount of moisture always ends up condensing inside the sleeping bag while you sleep.
If you do end up packing it up while it’s still damp or wet, you should unpack it as soon as possible, such as during your lunch break. Dampness doesn’t affect synthetic bags as much as down, but they still shouldn’t be packed away wet for more than a day or two.