To be blunt and honest, there is no reasonable reason to keep a system like Centos7, whose support has been out of date for almost a year, and therefore subject to security holes. Upgrade as soon as you can, if you don't want to make yourself and your client victims of cyber attacks. Right now Centos7 may already be subject to flaws that you don't know about, for the simple reason that they haven't been disclosed for almost a year, and they won't be disclosed anymore.
Regards,
Netino