Is there a limit to the number of units i can use? Currently i have 2, one is wired and the second wireless. If its possible to install more when can i purchase a single unit?

Hi @JasonHill, welcome to our forums! I suspect you might run into problems at some point if you use too many units but below 10 should work just fine.
If you'd like to use more I could ask my colleagues for some more information.