There are two enzymes at work, one which breaks the sugar chains in half, (again and again) and one which breaks the chains by taking one molecule from each end of the sugar chain at a time.
One of these works best in the 148F range, the other in the 158F range.
To get both of these enzymes working, we often mash around 154F. 158F will leave some of those chains behind, leaving more body/mouthfeel. 148F will convert more of those chains all the way to single molecules for the yeast, resulting in more conversion to alcohol, but a thin, watery mouthfeel to your beer.
Time is important because the enzymes need time to find all the molecules and work them - 10 minutes won't do it. Generally, 60 minutes is a good all-around time for a mash. Longer won't necessarily yield more maltose.