This query is a little different from the previous one from Apple.
As my previous posting says, it's quite common to say "since (X time) ago." Notice, however, that all the examples from Google have a specific past time point expressed, e.g. "since 12,500/two/thirty years ago." On the other hand, if the expression is an imprecise time period, e.g.,"many years ago," it's not so common to use "since"; it's more common to use "in" or "for":
I haven't heard anything about him in (many) years/for (many) years
If you want to use "since many years ago," or similar expressions, such as "since a long time ago," you should characterize the last time you heard from him with a when-clause, for example
I haven't heard anything about him since many years ago, when I read that he had gotten married
i haven't heard from my old roommate Kathy since a long time ago, when both of us were still looking for jobs