Ever means "constantly," "always," "at any time," "repeatedly." Every means "each and all without exception." Few speakers confuse these words except in the phrases "ever so often" and "every so often." Ever so often means "frequently," whereas every so often means "occasionally," "now and then." Trite phrases involving ever and every include "ever and ever," "ever and anon," "for ever and a day," "every which way," and "every now and then."
Dictionary of problem words and expressions. Harry Shaw. 1975.