There is no general set 'issue by' date. Except that each airline can set their own ticketing deadline and will auto cancel within a certain number of days

Res booked through TAs may have a longer life span before being axed. CX though is infamous for cancelling their segments by a certain date, or within certain dates from booking if you're travelling during a peak period.

Best is for a TA to take over your booking and extend the ticketing deadline.