Apologies if this has already been asked. When you build your fleet you choose your three fleet objectives like normal. Between games is there any way to change these? Say you want to try some of the new RtR ones but discover they don't suit your fleet? Are you locked into those objectives unless you retire your fleet and start over?

In the rules as presented, there is no mechanism to change them. They are part of your Fleet. You would have to start over.

Of course, there is always the Campaign Objectives to go by, and if you're always the attacker, its not like you use yours, anyway