As long as their arms - Idioms by The Free Dictionary
as long as (one's) arm (redirected from as long as their arms)
as long as (one's) arm
Very long. Typically used in the phrase "a list as long as (one's) arm." I'm too busy to make it to dinner tonight—I have a list as long as my arm of things I still need to get done.
as long as your arm very long. informal
as long as your ˈarm (informal) (of a list) used to describe a list with many things to do, buy, etc. on it: I’ve got a list as long as your arm of things I need to buy for the party.