Originally Posted by Mike Ward
When the light are down the diaphragm is being 'stretched' rearwards. When the lights are up the diaphragm is being 'stretched' forwards.
This is exactly right. So as far as long term storage goes it wouldn't make a difference.
If anything would be under stress, I think it would be the seals on the rod end of the actuator because these are compressed or rolled over in the down position. So, leaving the lights up would actually keep them in their natural state.
FWIW, I leave my lights up all winter long just to keep those old and possibly brittle seals from moving around too much in the cold weather when driving after dark.
Yes, I drive my car year round as long as the roads are dry.