Max T/O thrust is limited to 5 minutes, unless an engine fails in which case it is extended to 10 minutes. Normal 2 engine maximum thrust can be extended to 10 minutes by certification. This is often done for operations from airports such as Innsbruck where more than 5 minutes at fully rated thrust may be required (although in practice it usually isn't.) Assumed temperature is used to de-rate the take off thrust, so the point is generally redundant if you are not using maximum rated take off thrust.
Note that N1, N2 and N3 pointer and counter displays are inhibited from turning white to amber, if they enter the (near limit) amber band during take off or go around (TOGA) for 5 minutes after the band is first entered. However if engine failure occurs in that 5 minute period, the inhibit period increases to 10 minutes.
certificate data docs.