For ink pads as with stamps, and probably even more critical, proper storage is important. Ink pads should be stored in cool dry places away from heat sources.
The general recommendation is that pigment, resist, craft and embossing pads should be stored upright as the ink is thicker and doesn't tend to migrate toward the bottom of the pads, but will sit too thickly on the surface if stored upside down. And for dye ink and solvent ink the pads should be stored upside down to keep the ink on the surface of the pad. Stampin' Up!s flip top case design automatically stores pads upside down.
To extend the life of your ink pads you should always try to purchase a reinker when you purchase a stamp pad. Stampin' Up! sells reinkers for every ink pad they sell.
Many people who create with rubber stamps have felt top ink pads and have learned to bang and twist the stamps on the ink pads when they are inking the stamp for use. Usually you do not need to bang and twist. If you find yourself banging the pad on the stamp to get it fully inked this can be an indication that the pad is dry and needs to be reinked.
With foam pads, including Stampin' Up!s dense foam pads, it is best to tap the ink pad on the stamp rather that tapping the stamp on the pad. This allows for better visibility of the surface that is being inked and also allows greater control of the pressure when inking the stamp. One very important thing to remember when using a foam pad to ink the stamp is Never Twist The Stamp On The Pad!!! I can't emphasize this too much because twisting a stamp on the surface of the foam pad as you ink it up will destroy your pad, it cannot be repaired. I have witnessed the destruction of ink pads from this method of inking.
Reinking a pad is easy. Use zigzag movement horizontally from top to bottom of stamp lightly squeezing ink as you go. The repeat the zigzag vertically from left to right. When you have completed the zigzags in both directions you can use the bottle tip to go over the pad lightly with small circles to encourage the ink to go into the pads. That's all there is to it!