'Many a time' has really fallen out of use since around 1900.
Probably the the best answer would be 'many times'
I've used it many a time and I'm only 25.
I know a few people who still use it (including myself)
Glad to see I am not the only one who still uses "Many a", although it does not really make sense if you think about it.
Yeah I think "many times" is right :)
why wouldn't it then be "mange ganger"