You’d, ideally, not want to be looking up a word in every single sentence, but if you’re reading for ten minutes without anything new appearing, it’s likely too easy to learn from. But that also means you’ve learned enough to read that material for fun, which is kinda the point of all this studying.
If the sentence is just a string of incomprehensible kanji, but it’s an exception, I typically note it or take a picture and try to assume meaning from context, then start looking up the unknown bits whenever I have some time. If it’s just one word in a sentence, I’ll usually wait 'til I finish the page (or, in the case of a game, when that character stops speaking) to check my assumption.
If I can’t make sense of the grammar, I typically stop reading for the time being. If that’s above my level, it’s likely just a matter of time until the vocab is way over my head, too.
My ideal pace is to have around one lookup every five minutes. At most, one per page in manga. Anything more than that and I’m not going to retain any of it. But that’s highly individual. And it would not have been possible to achieve when I was just starting out.