I had to change blades today, shaves clearly took a nose dive and today's shave was noticeable improved.
Since I'm running two of these tests side by side, on in vintage Gillettes the other in a Gibbs Adjustable. I found that I got quite a few more shaves out of the Gillettes for some reason, the Gibbs was already getting bad after a couple of weeks. The Gillettes just started getting bad over the weekend.
I don't see any point in pushing past as it was a clear rounding of the corner and a couple of bad shaves was enough for me.
I've got pretty wiry facial hair, so it's no surprise to me. But it was absolutely worth pushing to find the limit as the shaves past week one were some of the best I've ever had, so I'll keep pushing blades further than I have in the going on.