rsclmumbai
I mean not necessarily. Some clients have over a million Tickets and still rocking and rolling. Just depends on your setup, resources, and optimizations.
No way to automate Ticket deletion. It's all manual; mass delete within any queue/search/user or per-Ticket delete within the Ticket view. In your case it sounds like you need to do Advanced Searches, Select All, Delete, repeat.
We will have archiving and all that stuff coming in v2.0 so stay tuned!
Cheers.