We also do quite a lot in EL; currently, the painting work is underway. Therefore, I can give a relatively accurate account of our time expenditure: On the last two weekends, my brothers, my father-in-law, and I were each occupied with painting work. If I divide the completed areas by the time required, I come to about 15 m² of wall surface with a single coat per man-hour.
At that time, the surfaces were already fully prepared and primed, windows taped off, etc. This effort is still additional, and of course, most surfaces will be painted twice.
We have a total of about 450 m² of painting surfaces that need to be worked on twice, so a total of 900 m². That amounts to 60 hours just for painting, plus the time needed for taping off, priming, and other wall preparations (we sanded all plaster surfaces once with the giraffe sander, marked all defects, fine-spackled, and sanded again). In the window reveals, we partially have superficial fine cracks in the plaster, which is why we decided to conceal them by embedding a reinforcing fleece into the paint. Thus, the work on the window reveals in one room takes roughly as long as painting the walls (this effort is already included in the 15 m²).
Furthermore, it must be considered that you have to organize the paints and tools, meaning first get an overview, choose a color, obtain a quote, and purchase everything and transport it to the construction site. Here is a recommendation: paints from professionals with the appropriate rollers are much easier to work with and provide better results than anything you get at the hardware store.
In total, without individual wall preparation, more than 100 hours will definitely be necessary to complete the painting work.
Regarding what a builder can manage: I have shifted my working hours at my job forward. This way, I have more time for the construction site in the evenings. At the moment, I spend four evenings during the week (about 4 hours) on-site, the whole Saturday (10 hours), and usually 4-5 hours on Sunday as well. That makes a weekly total of about 30 hours, which is quite demanding, but you know what you are doing it for. Also, it was not that much time all the time.
What stresses me the most is the preparation for a weekend when helpers are there. Everyone has to have something to do, the appropriate tools and materials must be available, catering has to be arranged, etc. That also consumes time and sometimes costs me sleep. However, you become more routine with it, and for the next house, you'll do it with ease :-p