They don't expire, so there's no real loss or harm in keeping them; eventually you'll probably get more.

Some have reported OK values in redeeming for magazines, but some of the options for using miles require a DL AmEx card.

There is a nontrivial minimum threshold (depending on ticket cost) for using pay with miles; this might require a DL AmEx too, at least for USA residents. For the record, tickets using pay with miles even for a tiny amount of money saved cannot earn miles or companion upgrades; they are treated as award tickets.