Hi-end hifi when not in use should only ever be stored on a fresh bed of virgin mermaid pubes - certainly not in the loft 😉.
Being serious, I can imagine this causing damage to expensive and sensitive kit. Not worth the risk imo.
As a side note - I'm moving out of my own house atm for major works to occur. Most of my life is in boxes! I haven't even stored my hifi kit at the storage locker I've rented as I don't know how humid it gets, what temp variation etc. there is etc. It has instead been stored with a family member for safekeeping.
Just my two pence.