Chems are great on first cleans but on maintenance it would waste more time than it saves.
Quite often I don’t even use chems on gutters/fascias cleans. I find cold water does it just as well.
I do somtimes give them a light softwash first.
To be honest by the time I’ve faffed about spraying Chems about and setting it all up, I could be half way through the job with just water.
I definitely think window cleaners have a tendency to over complicate things.
Recently just fisnhed a massive complex of houses and apartments. Render, facias, soffits and windows. We didn’t use any chems on the facias/soffits and found cold water did the job with ease.
Obviously it depends how bad they are, but to be honest, even then, good old water will almost always work. Being that gutters are plastic, they usually clean up very easily.