  The phenomenon of periodicity, discovered by Benson and Goodearl, is linked
to the behavior of the objects of cocycles in acyclic complexes. It is known
that any flat $\mathsf{Proj}$-periodic module is projective, any fp-injective
$\mathsf{Inj}$-periodic module is injective, and any $\mathsf{Cot}$-periodic
module is cotorsion. It is also known that any pure $\mathsf{PProj}$-periodic
module is pure-projective and any pure $\mathsf{PInj}$-periodic module is
pure-injective. Generalizing a result of Saroch and Stovicek, we show that
every $\mathsf{FpProj}$-periodic module is weakly fp-projective. The proof is
quite elementary, using only a strong form of the pure-projective periodicity
and the Hill lemma. More generally, we prove that, in a locally finitely
presentable Grothendieck category, every $\mathsf{FpProj}$-periodic object is
weakly fp-projective. In a locally coherent category, all weakly fp-projective
objects are fp-projective. We also present counterexamples showing that a
non-pure $\mathsf{PProj}$-periodic module over a regular finitely generated
commutative algebra (or a hereditary finite-dimensional associative algebra)
over a field need not be pure-projective.
