End-game Variety

[Exodus]

There is nearly no bt games with teams so well balanced that the game lasts so long. I never played a single game lasting as long as 3 hours and I did play quite a lot bt: There are just no teams which are so balanced, at least i never saw such ones. I can only imagine such long games when there are a lot of passive players in it, who "[...]don't know how to efficiently attack and destroy the enemy base.".

The teams don't have to be exactly balanced for this situation to occur. Also, I myself saw several games which lasted that long and also played them myself, both as the first attacking and defending side.
Defending is much easier, than attacking, because you got healing and shielding from your buildings and creeps. So even if the attacking team is a little bit stronger and was able to push the other back to their base, the defending team can use the easier position of defending to stop the other team. It's not unsual that the defending team gets more hero- and more creep kills, so they just have to wait some time until they are able to push back with their stronger equipment.

There are no games in which you are better, but "[the] push stopped right in front of the HQ and the enemy was pushed back again, because of player factories and such.". In my opinion this only happens if the attacking team makes mistakes and actually doesn't play well.

I don't think that this is true. As described above, the defending side has advantages. This is nearly everytime and everywhere the case, since you got a base for a reason. But it's also quite possible that this advantage is too high, by making the destruction of the base unnecessarily difficult, which may result in longer games or even a turnaround in power and map control.

The main reason I suggested this, is to reduce the game length. I'd even say that the 1:20-1:45 games are too long. Do you think by changing the winning condition this way, there would be an unfair advantage for the attacking team, besides the possibility to end the game faster?