Maybe. If you book and don't ticket, the seats are removed from inventory. Fare classes are allocated within a nested booking structure. Therefore it is safe to assume as other seats were also booked within the 24 hours, and that seat you booked will be allocated into another booking class once reintroduced into inventory. However, if it is far enough out and your still within tariffs restrictions associated with the booking class, you may be OK.

Typically I've only be able to get airlines to hold seats for 24 hours, sometimes with one 24 hour extension. If they allow too much flexibility, passengers would abuse the fare structure.