Will's above were 6 seconds and 3.2 seconds respectively, along with shutter speed however is aperture. The nighttime with complete dark are the easiest, as then you are only worrying about how bright the lightning is; Will's first picture above was an aperture of f/7.1 which is ideal for a decent distance and good bright CG like there was. Taking images during the day or when their is ambient light would require some adjusting in hopes that you don't blow out the sky or other areas of the picture. Will used f/18 in the second shot, which explains how he was able to still do a decently long exposure and not blow out the sky. However, as you also see the lightning strike is nearly as bright, which is expected beings it was in the daytime light.
It might take you a bit to get your adjustments right, but with time that camera will serve you greatly in capturing those lightning strikes.