I think, as so many others have noted similarly, that the time spent varies based on both your level of interest at that point in the build, your personal life situation, and what stage of the build you're working on. That's the short version of my answer.
The long version:
Though I'm retired, I tend to do most of my model work in the evenings, and a couple of hours is pretty much average in that regard. I tend to work on a couple of builds concurrently, so while planking a larger kit (the Victory), I'll put a couple of planks on each side of the hull of that model, and then slide into work on a smaller kit (the Red Dragon). I fire up SiriusXM on my phone and hook up to a BT BOSE speaker for background music as I fumble away.
But if it's been a long day, or the stage of the build is challenging, my time may be lengthened or shortened based on my patience or tolerance that particular evening. That said, there are points in a build where I'll continue working longer just because I think its essential to complete a specific phase. For example, if I'm running shrouds, I'll spend the time required to ensure I've balanced the work on both sides of the ship to avoid any potential warping or inconsistency in alignment. Ditto if I'm at a point where I'm really fixated on a given task... and the hours pass without even noticing it.
So, yes, the time I'm putting in varies and is all over the map. The key (IMHO), is not to force yourself to do more than you enjoy, as that will just create frustration and anxiety. Which in turn results in you not wanting to return to the model as soon as you might otherwise. If you're tired, you tend to make mistakes. So just do what you feel comfortable with, and like gambling, know when to say it's enough for the day (or evening).
