I've had a couple of older Charters - and both were good guns for what they were - carry a lot & shoot a little type guns. One a .357 the other a .44 Spl. - both on the same "Bulldog" frame - both 1970's vintage. I still have one - sold the other to a friend (and I'd never sell a junk gun to a friend). They aren't the sort of guns one would select to run thousands and thousands of rounds through. But at a couple of hundered rounds or so of factory standard loaded ammo per year, it should give you good service for as long as you wish to use it.
If the example you are looking at is tight - and there aren't any unusual clicks, squeaks or hitches when cycling it - $160 sounds like a fair deal (they sold for about $200 to $250 brand new). And do insist on dry firing it - slowly - at least a dozen or so times to listen and feel for these sort of things. It's my impression that the internal moving parts on the Charters are more prone to wear than barrels, frames, cylinders and such.
The basic design is strong and the quality of metals tended to be pretty good (at least on the older ones). If you look closely you'll see that the grip / trigger frame is pinned to a solid main frame (unlike the solid framed Rugers whose basic frame design they most closely match). So the "shooting loose" stories you hear about these have to do with those components loosening up - and wear on the internals. It's unlikely you will see one with frame or cylinder stretching (even if abused). And even when they do loosen up there isn't a concern about safety. You just end up with a rattely / squeaky gun.