How to age up in a timely manner while constantly producing villagers?

I've been watching ZeroEmpires' channel a fair bit lately and the competitive scene for AOE II has got me rather intrigued.

One of the things zero always says is to never have an idle TC, but how can you get enough food to advance ages if you're always spending food on villagers?

When I play I either have a decent economy and end up advancing ages after everybody else, or I can advance to the next age in a timely manner and have little economy to speak of.

Any help and/or tips would be appreciated.

Thanks!