General Protein Handling Question (freeze/thaw)

Hello

(please excuse any bad english)

I'm a nanotecnology student with a molecular background but without much
hands-on in that field.

I've ordered and received a couple potions of proteins and would like to
know some general handling of these.

Proteins comes either lyophilizised or in solution at ca 5C.
Is it normally okay to freeze the proteins again to keep their life-time
up even if they come in solution and does it depend on the protein?
In my case it is streptavidin and human plasma fibronectin.

I'm guessing it's okay to freeze them in diluted aliquots even if they
come in solution and no matter if they are in salt or salt-free, and
then thaw them just before use. My supervisor is a bit sceptic though.

Thank you for any help