Favours at work and in business have usually ended up having the opposite effect in my experience
That's my experience as well. Some years back I broke a personal rule of mine about doing favours and I made a consession for a likeable old lady who couldn't afford a small increase I made (So she said).
I suggested, "I'll do them evey other time for you if you like. Save you not having them done at all."
Mistake!!! Next time I went round I lost the entire block of flats to every other time. She'd gone round all her pals saying "He'll do them every other time if you like."
So I put them all up again as they were near a busy road and used to get really dirty.
When I thought about it, I thought what a fool I'd been. The woman chain smoked and was telling me she couldn't afford a small price rise, the first in three years. I couldn't help thinking about the cost of all those ciggies.
I didn't do that again!
Been pulled up a hand full of times because odd "mistakes" I've made. But when you compare the number of mistakes with the amount of glass I've cleaned in my time in the trade it's infinitessimal. Most of the time the so-called "mistakes" are dirt on the inside or blown double glazing and I've had to choose my words carefully when pointing it out so as not to make the custy feel small.