Now that its Summer I can't help the fact that make up just melts off my face!
I have found some products that really help with eyeshadow creasing though - Primer! Some primers are a little on the cosmetic side, creating a shiny look that doesn't help with making the shadow last.
I have found some that really do -
Urban Decay Primer Potion
Too Faced Shadow Insurance
Lunasol ( a Japanese brand) eye base
Art Deco (german brand) eyeshadow base
I apply them after moisturizing and I wait for it to dry a little. It really makes my eyeshadow creaseless and last forever. Its amazing!