This line popped out at me:
"'term limited' relationship"
I'm no expert, but, relationships aren't static and they are constantly changing and re-forming...there is no such thing as 'forever'...it could be, but no one ever knows what's going to happen...be it any relationship: from friendships to casual interactions and what not.
Unless you both decided that you are going to stop having sex with each other on June 24th at 9am :P then, just enjoy the moment, care for each other and for all people involved and just develop, evolve, grow? no?
and when things change....they change?