As someone who has done a lot of walking with my husband: Remember to be kind to each other!
Some days one person is strong, sometimes the other - and it's OK to share each others' burdens.
My husband can run rings around me when the terrain is hilly, and can walk much further without a break than I can, but I need much shorter breaks and can carry more weight than he can, as long as I'm fed four times a day - while he needs only three meals. When we get to the albergue for the afternoon, he needs a shower and a rest, I'm often still bursting with energy and will, after my shower, offer to take care of his laundry while he takes a short nap - and then he's ready to explore the town with me.
It's all fine, you don't have to do everything together, and there's no such thing as "fair", as long as you are both enjoying yourselves.
When irritation builds up, it's time to get a real hotel room and sleep in the same bed, which will feel like the utmost luxury, even in the most basic hotel.
Have a great walk together!