The requirements for list items is still evolving. I do not think that there are any formal rules that apply. My untutored sense of the meeting is that you have to fall back on common sense. My own common sense (being naturally the best) tells me that you would best follow the literary principles.
However, the Wikipedia entry on the topic is instructive and helpful.
Items—known as "bullet points"—may be short phrases, single sentences, or of paragraph length. Bulleted items are not usually terminated with a full stop unless they are complete sentences. In some cases, however, the style guide for a given publication may call for every item except the last one in each bulleted list to be terminated with a semicolon, and the last item with a full stop. It is correct to terminate any bullet point with a full stop if the text within that item consists of one full sentence or more. Bullet points are usually used to highlight list elements.
But what is the point of a bullet point? The word point is the clue. It is supposed to be short. Why? In order to make it easy to (a) absorb quickly and usually (b) to present as a readily assimilated and remembered list. Otherwise, Why use them in the first place. As the Wiki article points out, we are usually talking about somewhere between a single word and a short sentence. Shopping lists are the easiest (but scarcely call for any of the gallimaufry of little 'points' now available). They can extend to
phrases or whole sentences, when, for example, they are shown in projected slides as the main points being talked about in a lecture. Many say that they are overused for this purpose, and I tend to agree. The can the the main actions required to be carried out or the key conclusions. In this guide they can easily stretch to a sentence and may drag over to a second line.
They do appear as whole paragraphs, but, unless there is a very strong reason given, I should be asking myself "is this really part of a list?".
But what is clear is that this is a matter of style rather than of grammar or semantics. The only way in which it is relevant to English Language usage is that the use of bullet points may for some purposes licence the use of sentence fragments. You are allowed to write things like:
- Minds: physical or personal?
- Souls: real or imagined?
- Personal identity: a link to or separation from others?
Or it might be:-
In order to improve the quality of education, the school should:
- ensure that safeguarding policies reflect the latest guidance and are consistently carried out;
- repair the broken paving in the school courtyard and fence off the lake in the school grounds;
- make sure that pupils with a talent for mathematics are sufficiently stimulated and stretched.
Note that in this case, the use of bullets does not licence the use of non-standard sentence structure, but signals that each point follows on from "...the school should" and a convention has been used by which each point but the last ends with a semi-colon, and the last ends with a full stop.
I have seen whole paragraphs, but, in such cases, the bullets rarely are needed. In some such cases, there may be a case for using numbers as 'bullets' with the purpose of ease of subsequent reference. But again, this is not really a matter of grammar or semantics.