I very rarely cover Charlottes fitteds. Mostly she has grown out of them now, but even at they hight of use I only had, and still only have 4 Maz covers and I TB PUL cover and 2 fleece covers...For about 35 fitteds (and I wash both most of the time)
But I just found that if we werent going out anywhere there was no need to cover them.
She rarely wears pants here in Perth anyway, it is way too hot! So yeah, I see a lot of value in pretty fitted!

I just dont own many because they arent the most cost effective for us - we are AIOs (AI2s) all the way here