No I am definitely not saying that NHSEO stops getting links after a few days, it is all about how it is setup. I have profiles that were setup in 2012 that are still making links, ~1850 links in the past 5 days across 9 profiles with private proxies for posting and NHProxies for searching. Using a site such as Alexa for tracking your backlinks is not a good idea, read here to see why, link numbers from sites like that are meaningless.
If search keywords are setup well and everything else is correct there should be no reason to be making less than 100 links per day but if you are going by the number in a site like Alexa rather than in NHSEO you are not tracking the number of links made.
I will start to run a test with just public proxies just to satisfy my own curiosity of what can be done with pub proxies.