I DVR'd the Grand Prix but I did copy-paste all the lap charts so I could have virtual "live T&$" while I watched the replay.
Most Grands Prix are anticipation events: will the leader break? Will the cameras catch two backmarkerts battling? Oh, well, maybe next time.
Much easier just to watch one race, then the other, with only a single T&S screen open. But I will watch the start live ... as you say, that's 90 percent of the action.