8 plus years ago i bought 2 auto darkening units from HF. left one in the box and used the other for 5 years then it just up and died. No problem i've go the second one...it didn't work after sitting 5 years...can't change the battery in it either...crapi had to have a AD unit as i was upside down under a dash board no head nod would work there was no room to flip. Thankfully Tractor Supply had a AD unit on sale it was $80+ but thing works great. I can tell it works fast then the old HF unit no sand paper eyes after a few days of welding. I don't do alot of welding but when i do its a few days straight of fab work. then some Dos Equis. 
