You can create barcodes for as few or as little as required.
This means you can create;
per asset
per Asset Group (Suites)
for all Assers
Barcodes need to be shared with your Venue ticketing company. EH would much prefer to fully automate this process and wait for the go-ahead. Until then, you'll need to share barcodes using a file output and emailing that file to them.
This suggests you could create all barcodes for all Events as forward as possible. Perhaps building a full "code Season'. Barcodes can be exported across many events and where we charge by barcode - we do not charge where there is no owner set.
Remember Tickets can also be built in advance - or at least when all timings are confirmed.
Your company still has complete control of "tickets in the market" through the RELEASE process.
Tickets can also be rebuilt very quickly if there is a design or timing change.