writing style - After introducing an acronym, how faithfully must I stick to its use?

My average scientific paper contains about a dozen of acronyms. Some of them are really helpful: for example, it much more pleasant to write fMRI instead of functional magnetic resonance imaging.

However, I really dislike writing long sentences containing several acronyms. It makes the content difficult to understand for those who are not that familiar with my (sub-)field.

It would be sometimes better to write the acronym in full. However, how "acceptable" this is after introducing an acronym?

In long papers, I would also sometimes like to write out the acronym in full in a new section (e.g. when moving from methods to results and discussion). Some co-authors do not like that.

What is the correct thing to do?

(The use of acronyms (at all) is typically partly dictated by the journal I submit to. Most of them ask to use an acronym instead of writing the name in full if it appears at least thrice in a manuscript.)