Morn'ng, try this:  Just do one simple group, perhaps the top, render it, if that is okay, do another group, remove the rest.  See how it runs etc.

Of course save the whole nine yards first because you will be needing to try each hair group by itself.  It may be just one hair group that is causing the long rendering time.  Jan

PS just run the group by itself for about a minute.  If it takes much longer, go to another hair group.  Even on an old 2002 (one CPU, 5 MB ) computer, it should render in about a minute.