Care of mirror? Just like a pair of sunglasses.
Careful when cleaning they can scratch! Don’t use chemicals. Don’t torque the attachment point.
Usable temperature range approx. 40F to 100F. Most riders don’t venture out in dead of winter.
Storage? Store indoors in a cool location. Avoid thermal shock, do not venture into extreme temperature changes such as a warm house to a zero degree winter wind. Delamination may occur.
I recommend leaving the mirror on the helmet thru the season or year round unless you commute in all weather. I am developing a cold weather model.
Storage in direct sun or in a garage when it is below freezing is asking for trouble!
These are wearable art handmade mirrors. I store my helmet with mirror attached, either on a very sturdy wig stand, or with helmet upside down in a plastic storage box. Choose one small enough to let the helmet nest with the mirror safely hanging outboard. If you rinse your helmet after a hot ride, let it dry and drain into the plastic box. Avoid soaking the mirror.