Choosing a default angle

[Rossy66]

I have had my business up and running for just over 2 months now and although its doing quite well, I have a question for the forum that I know docent have a absolute answer but I will ask it anyway for guidance. I get a lot of knives that are in bad shape and although I have been looking up the website of the knife maker or Googling the answer, I try to put the factory recommended angle on it or a default 18° and was wondering if anyone who sharpens for the public chooses a different angle?

In all honesty, I would like to have a more "standard" angle to sharpen customers knives except for very specific knives that require a specific angle (As an ex chef, I use Japanese knives and sharpen most of them at 15° and have some as low as 12°) and I am wondering if the standard 18°  should be lower, possibly 15°? I understand that this may leave less material behind the edge and most cheap knives wont stay sharp for long  so is there a compromise edge angle? Any input would be most welcome.