Furthermore, having nuclear weapons means little if one does not have the equipment to make proper use of them. (blog.politics.ox.ac.uk)
So while this could help you preserve your Membership Rewards for a while, you may need another card to make proper use of them. (uponarriving.com)
There are also caveats about LinkedIn that don't fall under the category of etiquette, but they do involve proper use of it as a legal marketing tool: (lawyermarketing.com)