Imagine a channel where the initial secret for deriving of the actual key is established with ECDH.
First, that shared secret is used to derive a temporary key with some default parameters (salt, iterations) embedded into the software.
Then this channel is used to exchange random parameters specific to each direction (Alice sends to Bob parameters Bob must use to derive the key Bob must use to encrypt messages to Alice) and in response Bob sends such parameters [salt and iterations] Alice must use for HKDF to derive the key to encrypt messages for Bob.
Eventually, they exchanged these parameters and derive their own key per direction (Alice to Bob and Bob to Alice).
Can Alice and Bob after that exchange some parameters that can be used to derive IV and change it instead of exchanging the next key derivation parameters?
In essence, is it enough to send parameters for the derivation of the next IV with the message, at least for some time, or it is mandatory to change both IV and keys periodically if AES-GCM is used?