I assume you're trying to extend shelf life for a couple of days, not weeks. One possibility is dough enhancers, many of which improve shelf life. Most can be very easily incorporated into an existing bread machine recipe.
There are a variety of possibilities, and you can also buy commercially available dough enhancers that combine various helpful additives for you. I'd personally buy a dough enhancer formulation first, see if it made a difference in how my spouse liked the results, and then start experimenting with other (less expensive!) additives such as lecithin, gluten, powdered ginger, potato flakes, buttermilk, or more.
Searching for "dough enhancer recipe" brings up lot of suggestions which I can't personally vouch for, so I won't include one here :)
Changing the storage method can also help improve the longevity of a loaf. This is covered in another question; suggestions include covering the cut end (moisture escapes more easily there than from the crust), and pre-slicing and freezing the portion you know you won't get to.