Keeping a 5 month old up till 9.30 so I get to see him on workshop days. Bad idea?

Back at work a few weeks now. On normal office days I'm home by 6.30 and we get a proper evening together. On client workshop days I get back around 8.45, and by then the caregiver has had him asleep since 7.30. I get an hour in the morning, which is mostly feeding and getting him dressed. Twice this week I kept him up till 9.30 on purpose. He's cheerful until about 9, then completely falls apart, and he still wakes at 6. My partner thinks I'm doing it for me, not for him, and is probably right. Has anyone moved a baby's bedtime around a work schedule and had it work? Or do I accept that on some days I just won't see him awake?