Is it a good practice / policy to do this?

I noticed that my logs folder was over 6gb. So I stopped everything, purged the folder, and restarted.

1. Should I keep logging running normally, or only when there is an issue to troubleshoot
2. If I do keep it running normally, will a large logs file significantly degrade performance - cause Mezzmo to "hang", etc.

Logging does make Mezzmo run a little slower and does create large log files on disk.

So, you should only have logging turned on when Conceiva support staff ask you for a set of logs. After that, you can clear your logs and turn off logging. Do this from the Options dialog (Logging page).