There is a level of skill that I've not achieved when riding with my partner. She's fit, but due to a bad accident that concussed her, broke her clavicle, a rib, and collapsed a lung (I had a sympathy fall right behind going all @$$ over tea kettle but was otherwise un-scathed) she's very cautious of speed... Too cautious...
So, we'll be on some rolling hills on 360 and there's nothing but road in front of us and she'll brake the whole way down. Meanwhile I'm geared all the way up and am hammering or just enjoying the effortless speed of a downhill. So the gap grows. Instead of using that speed for the NEXT hill, now I'm geared down to a walk as I wait for her to climb and catch up... This goes on for a bit till we're back in the city... But that's for the training rides.
On our normal toolin' around rides to a HH, Barton, or the symphony, we stick close together talking and keeping cars from splitting us. There DOES seem to be a communication issue when we come to cross streets, however. Occasionally I've gone ahead when she wasn't ready and I'll get chewed out for that. Perhaps I ride more and as a result am more comfortable taking liberties with crossing, but I don't like her thinking I'm unsafe when I think it's just experience...
I hope I'll get better with the endurance rides when we have to just eat miles, but it's hard to brake down hills.