All the time. I only know this from having to log in every time the firewall gets behind and blocks the remote phones using responsive firewall.
I do think FreePBX is great, don't get me wrong. These are some the reasons I still prefer a freeswitch based deployment and enforcing domains as part of authentication. Almost all attempts to brute force authenticate are dropped simply because they don't know the domain (realm) being used and they quickly give up.
There is a lot more that I like over FreePBX in my current setup but that has more to do with trying to be a service provider.
For a single installation my only gripe is the way the firewall works, how do people use Bria and roam around. That being said they could close that gap at any moment and my only complaint would be the delicacy of updating systems or uploading the wrong format of an audio file. Which apparently only bigbear has ever had problems with. Lol.