the "sub mode" as you put it, Maddie, is, in my opinion, determined by the Dominant. It's kind of like sex, if you will, you're not always in the mood, but a proficient lover can entice you. Now I know that's putting a lot of responsibility on the Dominant, so I don't want all you Dom's jumping all over me...okay go ahead (LOL).
I have, however, noticed that when I am stressed submission is a nice place to go. What am I talking about, i'm always there! Geez, I'm probably over-stressed and not submissive at all.
And Warbaby - don't even go there with the age thing. ~smiling~ Don't you know that 60 is the new 50.