I've been given this advice and I'm skeptical. You can only mask things to a certain degree, it can make you look like you're hiding something (which you are), and the hiring manager will figure it out soon enough in any case. If they really want to age discriminate you're probably better off finding out sooner than later anyway. In any case, later career jobs tend to come from personal networks anyway. My resume was just a formality for any interview I've had in the last 20 years.