I can vividly envision Grant strolling along after passing the day's 46 km. mark, singing a song and enjoying life, while this 60+ grandfather will be happy to have found a bed after 22 kms. (my avg. day)
If one is fit for it, why not do it? Nothing wrong with that. As long as one listens to one's body (feet!); Ultreya! Each must do his/her own Camino. And as I understand it, Grant has also done "ordinary" Camino(s). So nothing wrong in testing one's capabilities. As long as it goes well. I have to share a story:
In Castrojeritz this April, the hospitalero told me about a young woman who came in 2 days earlier than me, having done 40 kms that day, and her feet were a complete disaster area, so much that they immediately proposed to drive her to Burgos hospital. But no, she only wanted a bed for the night, because she had planned for a 45 km. leg the next day...
And on she went: I do not know if she got to Santiago.
I am sure that Grant has estimated his physical abilities and is confident he can do it. The rest of us do what
we can/want.
Buen Camino, Grant!