Pluralising abbreviations question

[Moln]

How do you do it?

For example in a document 'active period' is shortened to a/p. Further along the document several active periods are referred to, should it be:

a/ps, or
a/p's

[OinkBalloon]

A/ps is ugly, but a/p's is plain wrong.

[TheGirlOnTheLanding]

Prefer a/ps to a/p's (as both words are shortened it makes no sense to have an apostrophe on the second) but far better would be A/Ps. Somehow clearer to have the abbreviation in upper case, although if that's not normally how it's done in this case you have to use the generally used version.

[CloserToFiftyThanTwenty]

I'd go with A/P and A/Ps

[CocktailQueen]

I'd change to AP and APs. You don't need an oblique. Define it at first occurrence: 'active period (AP)' then just use 'AP' after.

[GiddyOnZackHunt]

Definitely AP and APs.

[Moln]

Agree that a/ps looks ugly but a/p's is wrong.

I'd prefer no oblique but in the actual situation it's staying, sadly.