What would have happened if the husband then also slipped and messed up his knee and was unable to walk out? I see lots of potential "what if's" in this situation.

I would stay behind with my partner (esp. since they said they were well-supllied).

I'm sure I would have left our E.T.A. and hiking itinerary with a friend/relative and when we didn't call at the trailhead to say we'd arrived on time, they would have alerted rescuers.

I would not have left an incapacitated person behind.

However, I am very, very glad all turned out well for these two!

Man hiking 40 miles through wilderness to rescue wife is overshadowed by man walking 44 miles for beer
11:08 PM PDT on Tuesday, September 25, 2007
PLAGEARIZED from KIM HOLCOMB / KING 5 News

When Roxanne Tenscher tore up her knee on Glacier Peak, her husband Max hiked 40 miles in rough wilderness in less than 48 hours to get help. A feat completely undone only a few weeks previously by a Washington Native in the same area who hiked 44 miles in 11 hours… for beer.
SNOHOMISH COUNTY, Wash. – How far would you go for love? One man hiked 40 miles in extreme conditions to save his wife who was stranded on glacier peak in Snohomish County. While another treks 44 miles for Rainier Beer to re-supply beleaguered hunters in the back country.
Sherpa Dave, as he is known by friends and family, was with a group of 3 other hunters on a 9 day back country trip when he performed this feat of bravery.
“It was only 44 miles, and we needed beer” S. Dave commented when questioned about his heroism “I didn’t even drink any of em on the trip back in!”

But it wouldn't be easy. The trail is littered with downed trees from winter storms, and hot weather had everyone in camp thirsty and irritable.
"The real problem was, it was really hard to jog with 36 cans of beer, they get foamy and I did not want skunky, foamy beer at camp. I jogged out, but fast walked back in, which I think hurt my time..," said Sherpa.
Incredibly, he managed to hike dozens of miles without damaging or drinking any beer.
"44 miles on foot in rough terrain. It took him 11 hours" reported the happy hunters. “His feet were hammered, but I think they were that way before he started.

Upon returning to camp the hunters and Sherpa Dave were able to quaff a horrendous thirst
"We were really planning on spending the entire trip without beer," remarked one hunter, wiping tears away “but Im telling you, seeing Sherpa Dave come up the trail with that beer made my whole trip.

A few weeks later, the hunters and Sherpa Dave are back home relaxing.
They say hiking / hunting is still in their future, and now, they know how far they're willing to go for their love of the back country and for beer.
Sherpa Dave says there were times when he doubted his decision to leave the camp and strike out for beer, but rescuers and beer fanatics say in this case, it was the right thing to do because he had experience, good weather and sheer determination.
Rescuers encourage all back country hikers to carry GPS or personal locator beacons and have at least one member of their party “Sherpa Certified”

Hmm, assuming that their ETA was known by freinds/relatives, I would likely have stayed around as well.
If well stocked and well prepared you can hang in for a long time. Hiking out in a rush is risky, but warranted if there's at least one left in camp with the injured - not when leaving her alone.

Hopefully it is only the reporter who mentions "but no cell service". Mobile phones simply DO NOT work in the wilderness, because there are not subscribers enough to warrant a network build-out. NEVER rely on cell service when out and about.

As to how far? Any distance of course.

Always file a "hike plan" just like pilots file a flight plan; tell someone where you are going and when you will be back. If you don't come back, they can call SAR and have them come find you.

Even a long distance hike, call your friend at home and tell them you will call them in two days from the next stop on the trail.

The question was already asked; what if the guy fell and hurt himself or got lost? Now there are two searches that need to happen.