Cali Kings are known pigs. They will eat all the time if you let them. My cali was 16 inches long when I got him earlier this year and is now pushing 30 inches long and he is only a year old so they can grow rather fast! An 18 inch snake should not be feeding on day old pinkies. I would move up to fuzzies. You can feed the snake 2 fuzzies every 5-7 days. Cali's can grow rather quick and pinkies really do not provide much as far as nutritional value goes.You could even feed him 2 fuzzies every 3-5 days if you want just as long as he doesn't get constipated. If he does show signs of constipation you can cure this with a warm damp dish towel and a small enclosure for the snake. They will usually 'go' within 20-30 mins.
Like I said my snake was 16 inches long as of May,shed 5 times and is currently 29 2/3's inches long and is now ready to shed yet again. He moved up in prey size quick. I fed him pinkies the first day I had him and he ate 4 in one sitting and would have eatten more but I was out! I would have fed him fuzzies right off the bat but I didn't have any. Anyway he is now eatting large hoppers and small adult mice no problems at all. I'll feed him 2 hoppers or one small adult mouse on Saturday and by Monday - Tuesday he is out looking for food! I am only feeding him once every 7 days now but sometimes if my other snakes will not eat on Saturday i'll try again on Wed,and if they don't eat the F/T mouse then the cali 'pig' snake will be more then happy to eat!