There was some talk of this at BromptonTalk a couple of months ago. Someone said that replacement hinge spindles should come in designated larger diameter sizes than the original, i.e. +1, +2 etc, so that the slack of the worn frame area is taken up. It appears to be intended to be a factory job and I'm not sure how one would put a new spindle in. . . a thingy press is needed to deform the spindles ends. Dunno if there could be a home solution. . . perhaps there is a cheap hand-press device that'd work?