Zenfolio have a great online support centre where you can type in any question you have about using the program and almost be guaranteed an answer.
If you create a set of favourites whilst not logged into your account, you computer will store your favourites in its cache for one month. If you create your favourites set when you are logged in, the set of favourites will never expire unless you choose to delete them. If you have created a set of favourites whilst not logged in, you can still add them to your store of favorites within 30 days of creating them and they will then be stored permanently in your account until you choose to delete them.
When you're logged in, to check if your favourites are stored in your account, check the top right of your screen, if you see a button that says "Stored in your account", you know they are in your account permanently. If the button says "Store" it means they are not stored in you account, click the button to store them.
Yes, you can. You can select all or some of your favourites, then look for the button that says "Send to". A window will open with two tabs at the top. Choose the left tab "Send to a friend". Then copy and paste one of the links into an email.
Visit Zenfolio for more about creating, editing and sharing a set of favourites.