Been there done that
But as i said it all depends on the day and as i also said i'm less concerned about the overspeed condition, but anyway why push it? you might have someone in the other seat with little or no high altitude experience, so your sat there with a 9 knot margin and you take a toilet break, next minute chummy gets overspeed and out go the speed brakes and back comes the thrust, probably something he/she as never seen before, meanwhile your stood by the door (wrong side of) awaiting chummy to follow the correct procedure to let you back in.
Having looked at the CRZ/thrust/weight tables either our brand new aircraft are heavier than we think or have more drag than Boeing thinks
If you were flying above the FMC MAX ALT in our company and caught at it you'd be off the line, these limits & restrictions are there for the safety of the passengers and crew, in any event flying above OPT is normally counter productive unless your on a speed limit due slower traffic ahead at your OPT level
So never mind me being uncomfortable, why make your colleague feel uncomfortable? CRM is all about team work,with me i think you'd be flying single crew on the next sector, although it sounds like you fly single on all of them
