IMO gun ownership must be tied to both moral rectitude and a consideration of various medical issues. Moral rectitude be be firmly shown to be lacking when you're convicted of certain crimes. That's where a permanent ban can be enforced.OTOH a criminal indictment for certain crimes can call rectitude into question...which is where a temporary ban might be enforced.
As for medical...chronic,long term schizophrenia can warrant a permanent ban,Parkinson's Disease can warrant either a temporary or permanent ban.