depends on how this plays out. If the west gets it act together and helps Ukraine it may be postponed indefinitely. If they start making side deals with Russia

depends on how this plays out. If the west gets it act together and helps Ukraine it may be postponed indefinitely. If they start making side deals with Russia and ignoring Ukraine while they start taking major losses 6 months to 2 years. If full scale war breaks out between Russia and NATO 3 months (we will be to busy to do anything about it or they will think that). If nuclear war starts it to chaotic to tell, but if say its a limited exchange and both make it out unbombed and they aren't all dying of radition poisoning from the fallout whenever they want.