I too am interested in the answer as I feel like I am hitting a similar point on my bike.
General perusing of the internet though says otherwise.
Even though I am pedaling at max gear, I am not cycling at my upper tempo. This is evident by downshifting just one or two, and I am pedaling at a higher, more effective, more sustainable cadence. This probably means I am putting my legs under a higher strain by pedaling at max gear/slower pace,
and until I can hold the upper tempo while at max gears for the entire desired duration,
then I'm not really at the point where I am maxing my gear,
and thus am not at the point where I would need to up my gears to a higher ratio.
One other thing to note though is that even though I am not at the highest limits of my bike, I am also not using the lower limits of bike at all ever. Half of the gears on the lower end are completely unused, but that's probably due to my type of commute which avoids any major elevation climbs. I don't use the lower half of my gears and I'm commonly running on the uppermost 2-3 gear setups makes it intuitively feel like I'm probably pacing beyond the limits of my bike, but that is simply a mental (and probably amateurish) misconception since I'm not riding up large mountainsides(?)
You might or not be at a similar spot for your bike. But typically, if general reading is any indicator, unless your legs are spinning freely when they shouldn't be, it could just be a lack of cadence thus a physical limitation well before it's a gear limitation.
YMMV, as you are quite the bike miler rockstar around here, and this is just what I have gathered when inquiring about this exact same question with a much (much) cheaper bike.