Here's how things are... your customer gave you the machine for a repair, not to clean or wash... but you cleaned and washed... was it necessary to carry out the repair? Almost certainly not, you do it to add a differential to your work, but you spent time and at least water… congratulations, nothing against that.
But in the time spent for this “plus”, you could have sharpened a set or two of blades…
Yes, each one has its “hang-ups”…
I don't have your experience in sharpening to ensure that cracks only occur on the polished points in normal use... just like an automotive grinder shop, I prefer to use a chemical crack developer, as it doesn't hurt, it covers my lack of experience in the matter , in addition to my poor vision due to age.
I do not do the extra actually included things like cleaning even they are in for repair.
They only get the wipe down when they are in for a service.
The service includes blade sharpening along with the other typical general maintenance stuff but I want them to run like new (or often better) and look close to new also.
I do not wash them as I don't believe you should get water anywhere near s mower.
I wipe them down usually with WD-40 or silicon spray or a tire shine spray and then polish with a dry cloth so they are not sticky.
Typical time to do this is 70-95 seconds and it is last step after one is serviced and started back up etc.
I know the exact times it takes me to do all the typical things I do as it is very repetitious like an assembly line and I have time each action.
Again, I ask all those who clean, soak, wire brush, scrape, blades....how long does it take start to finish from the time the blade off the machine is placed in your hand to do a 21 inch walk behind mower blade???