If I remember right, We have tested with 5K connections on an 4GB RAM Win 7 machine and, out of these, we were doing approximately 250+ remote management operations. Hope this gives you a rough idea..
Additional Info: In ZENworks 17 Update 1 (17.1.0), JoinProxy has been enhanced to support more than 25K connections. So, If you upgrade to 17.1.0, you wouldn't have to perform the above mentioned steps. :-)