This topic was already discussed a few days ago, here or on the Hat forum.
You can leave the figures in boiling water for many minutes. 1 minute would do, though. No harm will be done to the plastic. I prefer to take them out of the boiling water with a spoon, and use my fingers to straighten or reposition limbs. Some might prefer to bend the plastic with tweezers while still in the boiling water. After cooling off, the plastic will stay in it's new position.
It seems to me the soft plastic spears provided are rather thick and so I decided to get some round section styrene rods (plastruct/evergreen) and flatten and shape one end. The result is smaller diameter and straighter - better quality but of course more expensive.
But there is one problem: some plastics have a strong memory - they will not stay in the new pose for a longer time (especially the softer ones). But every soft plastic (that´s my experience) goes back to the original shape if boiled.
I use the hot water treatment for Airfix U.S. Cavalry to get him to stay on their horses. I dip the trooper in boiling water up to his waist. I then hold for only 4 to 5 seconds, then pull out and squeeze legs, then hold squeezed figure under cold water.
Warning: Small pieces such as Airfix swords, sheaths, etc. will actually shrink-up under boiling water and will not go back to original shape. So test an extra figure first.