I approach this somewhat differently. I aim towards a maximum of 80 characters (including spaces and punctuation) per line. It’s an old-school rule from the print industry, but in somewhat of a rarity, it is a rule that is equally translatable across into responsive web design too.
Rules are there to be broken. But if I find the characters per-line measurement regularly exceeding 80, I’ll either adjust the theme settings to ‘squash’ the main content container narrower or interject the page design with a theme sidebar, columns or some floating content (like an image, pull quote or embedded video).
A width of 1070px might still be okay to use. But it depends what your characters per-line measurement is. That measurement itself is influenced by factors like font size, font weight, font family, letter spacing and CSS box model etc.