The same with all Feruchemist metalminds, the larger in size and the more pure in their metal composition, the more of an attribute they can store. A small ring can't hold as much as a large bracer. So while storing an attribute can be limited physically by a person, the metalminds can also be just as limiting if not more.
Also, continually storing an attribute can be limiting if you use it too much. For example Atium stores age, but can't make you immortal, as stated in the Coppermind Wiki:
"Also, while able to extend their life greatly, someone Compounding atium is not truly immortal; over time, the amount of youth that they would need to consume (and the amount of atium necessary to allow them to do so) would increase beyond their ability to generate and store it, besides outstripping their physical ability to ingest and burn it."
Overall Feruchemistry does have its limits. Hope that helps King.