We're well aware that the amount of energy Spirit & Oppy receive from the Sun is declining during autumn and winter due to the position of the Sun and the shortening sols on Southern Mars.

Do ephemeris tables ( Sunrise/Sunset ) exist for ?

You can generate them using Mars24:
http://www.giss.nasa.gov/tools/mars24/

Also, if tables are easier, i've uploaded the sunrise/sunset times for Spirit and Opportunity through sol 3000. They were calculated using NAIF libraries (and a simple driver routine). Sunrise/sunset is determined by the sun being within 0.03 degrees (or something like that) of the horizon using the Mars reference ellipsoid as the horizon. Sorry, I was lazy and did not compress the files.