Also, it is probably more effective to make sure you get to a new level before heading to Sentinel Island, so you get a full level bonus. Mindreads are essentially free at that point, since you get however many experience points you need to reach the next level (so getting to as high a level as you can also helps; in D2:ED I made it to level 18 in the fjords), so you might as well take advantage of that, but it is not a huge effect compared to the amount of experience you need to level.