Academic writing: Referring again to the works of authors et al. Does date need to be included every time? If I were to refer to the work of X et al. [YYYY] several times within a paragraph does one need to write the date every time? It appears to disturb the flow of the writing and reads better without, however I'm unsure of the convention.

I've never taken notice either way when reading papers and cannot find an example. Perhaps it is bad form?
This is entirely dependent on the venue's style. It varies not only by field, but also by the particular journal or conference.

Ideally, your venue will have a published style guide.
Or at least a short document with explicit instructions.

Sometimes this will be in the citation style guide, other times you will need to look in the full guide.

Failing that, go digging through other papers published at same venue,
and see what they do.

Failing that, or if this isn't actually targeted at a standard venue (eg for a standalone book). Find a style guide, for your field. Either one used generally used in your field Eg the Chicago Manual of Style. Or choose on from a journal that you like.