Yes that is probably true to an extent, spending alot of time together sort of dulls the passion a bit, you do not need to miss eachother, the gift of wanting to be with someone, but not actually being there physically is powerful because it creates a want that you cannot fulfill.

If you want to bring the spark back into the relationship you could try having a break for a fortnight or so, and you may appreciate eachother more. Or alternately you could try seeing eachother less, or doing new things.