from my experience , Im not an expert and dont advertise as so, but in many cases the customer has some input...usually a financial one. I recommend x but they want y because its cheaper, I want to do A but they want B because it involve more time and money.
if a bike has been stood for a while, my T100 for instance, the ethanol has eaten away the brass jets, Ive put the carbs aside and bought a new pair, bolted straight on and ran a customer would just want new jets, preferably without the ultrasonic clean first then complain its not running right. believe me when you are working on a 1980's Japanes 4 cyl with hard inlet rubbers,you only want to take them off once, so its strip clean and replace parts then refit. 2 hours minimum, then they come in with a second hand set from ebay.
my local MX shop are great at their make but a road bike ....Ive still got the engine they rebuilt the top end on which went the same way as the replacement work they did. on removing the head there was a shim floating under the crank, I cant give a garantee on another top end rebuild unless I strip the complete engine,