Hi Jim,
Well... Each of these requests is pretty custom (at least from my experience with them) and they can be implemented but sometimes the # of responses to based on the UserID, sometimes its based on a timeframe (for example, if you vote on one of the recent contest entries at
http://www.datasprings.com/contest/...st-entries which stores your IP Address and only allows a single vote every 24 hours), and sometimes its based on something else such as what this user might want which is a total # of submissions received etc... This can still be done (as is easier then in 2009) via a SQL Validation option however there is not a build in feature to do this. There are other instances where you might want the ability to submit an entry form until something like "a class" is full and then after that class is full the list of available classes no longer shows that item within the list....
So... Each situation is pretty unique from what we have found, and each one requires its own sets of rules and workflow which (for the most part) our module can already handle. There is a built in feature to enable "Survey Mode" which only allows a user per IP address to vote one single time, but, to answer your questions there is not a feature to allow for a "maximum number of submissions allowed" etc...
Thanks for your questions, I welcome any feedback you might want to give us!
-Chad