If this was a 'store' sales person providing such ridiculous information,
the store should consider retraining him or keeping him away from products
he knows little about.
If this was an actual 'Canon' in-store product representative, next time you
see him suggest another line of work.
This of course after you talk his supervisors name out of him so you can let
them know what an idiotic piece of advice he/she gave you.
Canon (and most other manufactures) printers will park and cap the printhead
shortly after the completion of a print job. In the case of Canon printers
made in the past 4-5 years this takes place approximately 45 seconds after
the last print command is received. If you reach up and turn the printer off
using the switch on the printer or via auto power off in the software
driver, this will also cause the printhead to park and cap at the home
position.
So, providing you do cut the power to the printer in an unusual manner (such
as turning ff a power strip it is plugged to), before it gets to complete
its normal capping procedure, then the head is capped to reduce the chance
of clogging.
It would generally take many weeks of no use before a clog 'may' occur, and
even then a simple head cleaning cycle or two should clear it. IF for some
reason you are experiencing more frequent clogs (say after a day or two of
no use), then service of the printhead or printer may be indicated. To turn
the printer on and off needlessly would be a waste of ink and un-necessary.