Matt Whiting wrote:

Good explanation but you forgot to factor in corrosion of those
blades. By the time you reach 1700 years, the first 1200 years of
blades would have corroded to almost nothing. This would give at least
another 500-600 worth of storage. You can calculate out the rest....

Except that iron oxide takes up even more space than the iron ....

OMG... there may only be 1000 years of capacity. Time for an emergency AD!