The clime time for my robot was about 8 seconds ± miliseconds.  My robot works
by having 4 individualy powered wheels pushing against the walls because of two
other motors extending the four "wheel arms" until the robot it tightly stuck
between the walls.  Then the two arm motors stop, but the wheels continue.  The
robot then cimes up the walls using the turning wheels.  For the pictures, I
did stop the robot every 1/2 to 1 second to show how it worked.  I did not
attempt any extra credit.  The walls I used are exactly 1 foot wide and 1 foot
tall made of plywood.  The robots main part is made up of 8 large technic
turntables that hold on the arms and make them extend.