I say "Hey, let's go for a ride." If she doesn't want to go, she tells me to go have fun. She knows that it takes the stress out of my day, so I will be happier when I get back. As far as time, I just tell her how far I plan to ride. She's good at figureing how long it will take. Now, on the other hand, you have to give to get. So try to encourage her to take time to do whatever it is that makes her stress go away. If you have kids, this means you get some "be a great daddy" time.
Hey Hon! I going for a ride!, Then I'll ask if she wants to roll with me, and sometimes she go and other times she'll say "Have fun!" My wife is cool like that. right now, working on getting her own "X".