I have thousands of attachments on my JIRA system but I don't think it affects JIRA at all. You can say the same with system performance too.
In addition, your best way to handle this is to assess on what you have:
Base on this, I think you can assess how much growth and till when will your system cope up with the growth. This is just for the size itself not performance,
It looks like you're new here. Sign in or register to get started.