On fair-weather photographers The photographer who is unable to adjust to the conditions of the day is only a photographer on fair-weather days. In every profession, you could restrict yourself only to days in which conditions are correct for you to engage in the activity. You might only write when inspiration strikes, or produce art only when you have a feeling. The problem is when you cease to produce simply because one or two conditions of yours are not met. The photographer that has a bad day of lighting must learn to adjust and continue to take pictures. The pictures will turn out just as good as before due to their ability to improvise and find solutions to the problems. That is the ability you should strive to cultivate—have so much skill that circumstance doesn't restrict you from continuing to work. From Pressfield you learned to write only when inspiration strikes... and inspiration strikes every single morning, at 5AM sharp.
On timelessness There are many books that you read or have read in the past that you immediately know to be timeless. These are the sort of books you should aim to write. They don't go out of style because they were never in style. They were not made to be in style or with the times. They were intentionally created for whatever purpose they once needed to serve. Aurelius's Meditations were produced for himself, and that purpose is clear throughout the entirety of the writing. He had no considerations on how he could make the collection of writings sell more copies. When we pick the book up, since it was written with such clear purpose, it fulfills that same purpose in us as well. That is the beauty of a timeless book. Aim to rid yourself as much as you can from timeliness in your writing. If you absolute must be timely in your work, make it separate from the main work. Put it in a footnote. Don't ruin timeless.
On style versus taste There is a clear difference between style and taste. Style is timely, while taste is timeless. In order to be stylish—in fashion or in writing—you must be of a certain time to emulate a certain time. In order to have taste, you must be of humanity itself. There is a reason that Dylan's lyrics are so classic: love will never go away so long as humans continue to exist and reproduce. Love is a part of humanity, not part of an era. Boil down all timely matters to their principle and you will find at the core human problems, not problems of a given time. The ability to do this in a creative endeavor is taste. It takes practice, resolve, and discipline to do so, but it is the only way to create things that can last forever.