You could stay in SM up until 44 I think, but the exp starts getting really slow. Maybe 20% a level at 43 and you can only do the Cath wing.

I used to just do the Cath wing as it's the quickest. However, if you want to avoid hitting the instance per hour cap, then clear all three wings. In your low 20s a full clear of SM will get you about 2.5 levels.

A couple more things I figured out... your slaves can stay at the entrance of Library. You can clear the whole instance and not move them one and they'll still get exp.

For the armory, I keep my slaves where they are, kill as I go (feral tank) up until the second pair of stairs (the last stairs before Herod). If you go up those stairs, you will be out of exp range for your slaves. Before those stairs, your slaves are within range. Once I clear everything up to the stairs, I then stealth to Herod and drag everything back to before the stairs.

For Cath I just kill everything outside the actual Cath, and then pull the entire Cath to right outside the Cath.

That system allows your slaves to never move in SM and the only time you're not killing as you go (less durability wear on your gear) is for the short distance from Herods room to the stair case.