You can reverse it, but only one time. I downgraded my account a while back but if you "Enhance" (Pay Pal's friendly word) your account back to a "Premier & Business Account" you are stuck there. I guess you could close your account & open a new one to get around their rule but what a pain.

Here is Pay Pal's help page on the subject.

https://www.paypal.com/us/cgi-bin/webscr?cmd=_help&leafid=1405

Cheers!
Bill