Of course, it's unrealistic to think that every single time you happen to have your long time mate in your view that you will continually be thinking of that ~heat~ but do you still catch yourself.. In those moments when you take a look, when they are unaware of your gaze.. do you still think 'oh yeahhhhhh'... If you do have those moments of desire for one another that's a step ahead of most people in long term relationships I'd say. Too many people settle into the dreaded comfort zone and ignore that the fires still have to be tended to, to keep the flames burnin'. It's risky to assume that any of those feelings of attraction are to be taken for granted.
Take time to gaze at your partner.. how does it make you feel? If you carry the feelings of attraction and desire forward in your relationship.. if they are lasting.. you've got a good thing going..
Next step, make sure you *show* your mate how attracted u still are... and enjoy!