Teflon is a remarkable substance. It has the best resistance to chemical attack of any polymer, and it can be used at any temperature between -73 C and 260 C with no effect on its properties. It also has a very low coefficient of friction.
A stale dated warrant is an unredeemed warrant which was issued more than six months prior to the current date. A stale dated warrant is expired and the original instrument is no longer negotiable.
Expire is not really the right term; but effectively yes. In general a cheque older than six months will be considered stale-dated and will not be honoured. Reference the Canadian Payments Association FAQ.