What is the time period of Cache

Page is not found and no links also but cache exists

[AjiNIMC]

There are pages which are removed from the websites some 6 to 7 months back but still the cache exists(which is same 6 to 7 months older) .

Isn't there a cache expiry period for Googles and Yahoos? If no link to a page exists or is not submmited won't google check it time to time?

Aji