Are all divine liturgies about two hours? Does the time differ by church (Romanian vs. Greek vs. Antiochian)?
Do they differ for holidays?
Lots of factors that can influence that. I would say we usually run a little more than 2 hours.
*If the readings are done in more than one language
*Sundays of Great Lent can be a little longer too because: the Liturgy of St Basil is a little longer in some of the priest's prayers, communion of the clergy takes longer because of preparations for the Presanctifieds coming up later in the week
*musical arrangements selected by the choir (this can make a huge difference)
*length of homily, ours is usually 6-7 minutes
However, it is a little less than 1.5 hours when we do all English on the occasional Saturday due to: fewer communicants, simpler choir arrangements, and the readings not repeated.
Another question is does it actually start on time, because if it starts late then it seems like it is even longer. Russians also tend to love to do Molebens right after the dismissal, before the kissing of the cross, so additional services routinely done after, but attached to the liturgy can make it longer as well.