Well, I don't have an arena, so all I can do is trail ride, unless I'm at PC or a competition. Which means that I have to get my horse competition, show-ring ready while riding trails :]
My rides are a mix of fun and work. I'll ask for a few steps of collected trot/canter/ here and there. I'll sometimes randomly stop, haunch turn/rollback/spin and keep going. I'll leg yeild him through trees, jump bollards, etc. If I find a nice flat spot, i'll do some circlework for a while then continue on. When not doing the above, I give him all the rein he wants, and the only things I insist on are straightness, and maintaining the gait I ask for until I ask for something else.
I also agree with letting ANY horse have a good run every now and then. Most rides I will let Bundy have a good full-on gallop. It stretches him out, and works muscles that otherwise don't get worked. I also need him to have a level head during fastwork, for campdrafting and working classes, so doing it regularly just makes it part of a ride; Nothing to get excited about.