The question is not precise. If you make a 80Nm flight hop between two airports you will never reach cruise speed. Example ZRH-GVA with MD11 each Monday morning (aircraft positioning).
Cruise speed may change during the flight due to unforeseen circumstances prior to take off.
Cruise altitude changes during the flight when ship gets lighter. You start FL310, you may finish the flight at FL370. Or if the wind forecast was wrong, you may decide to fly lower at a different speed.
Computers are calculating during the climb the best speed, thrust setting to climb using temperature, wind forecast, fuel price, cost of operation. So your TOC could be anywhere. If you have engine anti ice on that is changing too.
Since the question is not precise, the answer is not precise either: Make it average 2000 feet per minute and you will have your time to "cruise alt".