Christians have been talking about the Great Tribulation from the moment that Christ proclaimed its coming. It will be the most horrifying and awful moment in time, since the beginning of Creation. It will be so bad, that you would rather die than go through it.
That is COMPLETELY understandable.
Likewise, it is completely understandable to want to know how long the Great Tribulation is. If you are going to go through it, you’d like to know how long it will last.
Horrible times are always more bearable, when you know when they will end.