Formscentral doesn't really support having multiple users complete a single form. While you might be able to use the Save form feature to approximate this, it isn't a recommenced workflow. Email receipts would allow users to get a record of their responses. And lastly we do support up to 5000 responses for a plus account form. I am aware of other customers who are using our product to collect performance assessments, however they don't require multiple users to fill the same form. My best suggestion is to look at Adobe's Livecycle product offering for your solution.