Recruiting Timing

So I've compiled a list of contacts/phone numbers/email addresses for recruiting for next summer.

These consist of bulge bracket banks, middle market/boutiques, private equity firms (big ones) and small ones.

I've read a lot about how it seems as though these companies, according to their size usually, recruit sequentially (unless I'm wrong)? Thus, big banks recruit first, followed by boutique/middle market, etc?

If this is the case, do any of you have a rough estimate of when is a good time to begin reaching out to these places next fall? Would you go about it all at once or follow some order?

Thanks!