If part of the cooling system is warmed (deep cold waters that well up various places) then the whole system eventually warms to a new higher near - balanced temperature. (skepticalscience.com)
Xapo maintains over 97 % of all its customer's funds in deep cold storage, providing a higher level of security than most customers could provide for themselves. (blog.xapo.com)
There are approximately 16.5 m bitcoins of which ~ 4m are lost, ~ 4 - 6m are in deep cold storage, ~ 4m are in cold storage and ~ 2 - 4m are salable. (thereformedbroker.com)