When do companies typically have intern positions filled?

I'm completely new to every facet of the banking/finance/consulting industry, but I'm graduating this with my bio-chemistry degree and was looking for ANY internship that could expose me to any "business-related" career.

Lazard contacted me saying that they had chosen someone else; Deloitte has contacted me for further information and has been infrequently speaking with me; Northwestern Financial Group contacted me to offer me a spot.

Is there a set date in which I will have heard from all other positions that I've applied to, or should I have heard something by now from everywhere?

And if it is a bit early to have heard from everywhere, should I accept the internship at Northwestern FG or wait for others? I've heard that they basically hire interns to cold call and sell insurance, so I'm not certain of the pertinence to what I want to do, but it's still a position. If I'm not going to be offered anything else I figure I may as well do it.