I myself regularly use view and session scope variables.
Depending on the variable use depends on the best scope to use. Hopefully this might be of use
requestScope
This only last for a single request. Object is a Map (lookup with a key) so you can add your own values but you need to make sure you don’t overwrite existing values.
viewScope
Setup variables that exist for the life time of the associated view (Xpage). Only visible to the current user. Lost as soon as you move to a different page.
sessionScope
These last as long as the user’s session is active (lost if you rebuild the application). Only visible to the current user and exist between all pages
applicationScope
Available to all users and are available while the application is in server memory. Good for global settings where the same parameter should be used by all