Sitting and learning all day is the ideal. “Talmud Torah Kneged Kulam.” Chazal say, one word of Torah is higher than an entire lifetime of doing these Mitzvos. Chazal often mention that Toroso Umnoso is the ideal, that we do nothing all day but learn. Nowadays poskim say that we cannot reach that level, but clearly the closer the better. Also, Shulchan Aruch Hilchos Talmud Torah, in the Shach, says that nowadays learning all day is the ideal, and that if someone has the ability to do it, he should. The Shach adds that regarding learning all day in general, nowadays we cannot reach our potential in learning the way the Rambam etc. did, since we are not on that level. Therefore, we should learn all day if we can.
The Rambam writes that a “working person” is someone who learns 8 hours a day and works 3. Not works 9am to 5pm.