Balloon decorations that used inside last a week and you always get spare balloons and a short explanation on how you can replace the leaking or popped balloons yourself.
Balloon decorations outside are generally less durable because they always influence external factors such as people touching them and the weather.
Balloons catch a lot of wind and balloons can not stand the full sun (light colors better than dark colors).
Rain makes helium balloons wet and therefore heavy so that they come down to the floor early.