Lettuce: Just a Cool Weather Crop

This is my last planned planting of lettuce for the spring season.  I have a scheme in mind to see if I can have a prolonged growing season for my lettuce.  I've planted these plants in an area between two tomato cages.  I can place shading supported by the cages to lower the amount of light the plants get.  Additionally, I will hand water these plants to make sure they are getting consistent moisture. 

I'm looking forward to seeing how long these lettuces will last into the warm season.

Have you had any success in elongating your lettuce growing season?