My congratulations!  Daily is better than once a week, in fact, I calibrate
before every pH run, just to make sure!  and if I do a higher pH (pH 9 buffer)
and then a pH 7 (pH 7 buffer) these would both be calibrated for their pH
range, and I also look at room temperature, the calibration buffer can read
differently at 25C vs 30C, beware of reading cold buffers!  Check the buffer
bottle as some have temperature range vs pH on the side. 

Absolute correct calibration would be to calibrate with a buffer, do the
reading adjustment, then rinse electrode and recheck the calibration to
make sure it has not gone off.  Tedious, yes, but we like to make sure!!

Gayle Callis