I just want to make sure all submissions will stay in my in boxes I want to keep all information

Just confirm that all my information that is given to me through my clients will stay in the inbox for an unlimited time? 

Thank you 

That is correct. The data will remain unless you deleted form submission data or deleted the account also.

It is also possible to make a backup copy of all your account data.

Guide : How to Export All of Your Data at Once

Please let us know if you need further assistance.