Hi Jean,
There isn't a requirement within the upgrade document for this, the section to check is the Upgrade Checklist (Pages 89-94) in the below document:
https://support.symantec.com/en_US/article.DOC9500.html
Thinking about the question, you could see interruption on your clients if you're applying software updates at the time of when you're upgrading the SMA. The SMA often closes during the upgrade process, which would interfere with your software update and possibly cause it to fail. As long as this is fine, I don't see a reason to disable them. From experience, I have performed many upgrades for customers without this ever being an issue.
Thanks