[megous]

Yes, you can maintain your fork for perpetuity if you can't/will not get your changes upstream. Why is that a problem?

If you're using any complicated FOSS professionally and you have SLA with your customers to say fix issues within day or two you don't have a choice anyway.

[IshKebab]

> Why is that a problem?

Because it's a ton of unnecessary work. And because of the other reasons I said.

> If you're using any complicated FOSS professionally and you have SLA with your customers to say fix issues within day or two you don't have a choice anyway.

This is true. I always try to upstream patches anyway though.

[necovek]

How do you define unnecessary work if this is... necessary for you?

You are already benefiting from getting the tool/library/system for free, so you can still compare writing the thing you need (necessary?) from scratch or adapting the FOSS solution — maintenance comes with both options.

When you invest enough and are lucky, someone else might just fix the thing for you or pick it up and maintain it for you — but do not count on it, and you are good.