Legally you have 30 days to return faulty goods for a full refund, although if to 'inspect and accept' the goods reasonably takes longer you may be able to extend this (e.g. hidden blowholes appearing in a casting), but you should still have proof of purchase.
To be fair to Reeves, my experience is that they will happily replace faulty goods with a receipt beyond the 30 days (in fact they let me keep the faulty casting).
On another occasion I had a casting I had for a few years with no receipt and they wouldn't replace it, which was fair enough – I should have spotted the fault the day I bought it.
Bear in mind that the unscrupulous may pick up castings or parts at shows/boot sales and try it on.
Neil