@THUNDERELVI & @Inception_AC both claim to use no proxies so maybe they can chime in - I've spoken with Elvi and he said he's rolling IPs every few minutes (something which most places on the planet can't do, so probably only a handful of providers would work), basically your batch script that releases your MAC and reconnects also needs to be incredibly quick otherwise you're going to see all sorts of timeout errors on MP actions. The computer won't really be useable for anything other than MassPlanner posting since the connection will be up/down every minute or two and your provider needs to have large dynamic IP pools/let you refresh IP every couple of minutes.
Any type of hiccup, non-release or failure to grab a fresh IP can result in any accounts performing actions getting linked and IDed because of management IP. I've seen Inception talk about bringing fresh accounts online so he might just be replacing whatever get's hit and going churn & burn, he hasn't posted much about FB Groups in a while and what has been posted is talking about bans/issues.
Personally some of my oldest workhorses are over 18 months old and have been posting that entire time without even a PVA request, you can churn and burn or go for stability. Max ceiling on an IP cycling type of setup would be 100-200 accts and you're taking a lot of risk, can only work in certain GEOs/ISPs, etc. personally I'm not a believer in the stability of it for group posting but I'd love for Elvi or Inception to prove me wrong and shed some more light on the subject.