jgarciaepncorinto
First things first you would definitely need to create a new Ticket Number Sequence so it can be Incremental instead of Random. Then you would set this Sequence as your Default Ticket Number Sequence under Admin Panel > Settings > Tickets.
Now, once the year is over and you want to export the Tickets you can do so via the Export feature at the bottom of any Ticket Queue and/or Advanced Search. Additionally, to get the full thread, metadata, attachments, etc. you can Print each ticket to PDF; this has to be done for each Ticket individually however. Otherwise you would need to do a database dump.
Lastly, once the old Tickets are deleted and you want to reset the numbers you can go to Admin Panel > Settings > Tickets, update the current Sequence, set the Next field to 1, and Save Changes. Once you update the Next setting to 1 for the Sequence the Ticket Numbers will start at 1 again.
Cheers.
