1)It all depend on programming technique, you can save power whenever motor is not being used
2) LDR are sensitive dust. When Some dust fall on it . it might not work. It need periodic maintenance
3) 0.003 deg mentioned is not per degree to moved in everyday. I mentioned because if we use simple code using LDR after year if you reading 30deg for particular time , U might degrade to + or - 5 degree after year on same time, If we calculate for long period track will be out of position.