Not Charity but theres always the chance as people do collect them but Bargin as in Poundland etc, still occasionally get a tin and lighter together...
My Grandad was often to be found with a Golden Virginia tin in his pocket, I think he kept it once he gave up smoking but Grandmothers likely binned...
If the tin is sealed I don't think it's a problem at all, once the tin is open they will start to oxidise because it's a natural reaction, but again...
Never considered this an issue. As long as they are accurate I just use as they are. If any are grouping badly they are used for short range plinking...