We prefer to keep all tickets in the system as we have users who are using quite old versions of our products. These tickets help us locate old issues and provide to-the-point answers. Additionally, old tickets help us escalate features which have been requested in the past.
For these reasons, we are not sure that we will offer the possibility to delete old support tickets. We do plan to offer an Archive folder which will help you put some old tickets away. What do you think about this? Will this help?
To some extend, we are a little like Gmail - nothing is to be deleted. At least not yet :-)