I didn't say anything about being able to walk in them. Of course, if you can't walk in them they are kind of superfluous as footwear anyway, but that is really beside the point. I mean uncomfortable. If your toes get tingly after about an hour, or if you were to go dancing in them and find that your feet hurt and you have to take them off part way through the night and dance barefoot, or you get home after wearing them all day and when you take them off your degree of relief is more than usual, then you are doing it wrong.
If anything else hurts (knees, hips, whatever) you shouldn't be wearing them at all ever, like my sister who has a wonky hip socket and really can't wear heels at all. Being comfortable in heels is a two-part dealy, because even if the shoe isn't too tight across your toes or too short in the vamp for your longest toe (which might be your second toe, which can create problems if you get the wrong style) and it isn't to tight down the shank and the back of the heel doesn't rub blisters onto your ankles, there is more to it. Sure, that stuff is nice because it means it won't give you corns and bunions and make your toes numb, but you have to have leg strength for it, too, and I don't just mean in your ankles. It affects your knees and your ankles directly, so your calf and ankle muscles need to be able to take the brunt of it, but your quads and hamstrings are also key players and if you don't have the muscular capacity for this, it is not a fashion thing anymore and it is nothing personal but when I say you shouldn't wear them I mean because at that point it can be dangerous.
Something else people don't think of is how it changes your posture. Have you ever gotten back pain a day or two after wearing your heels for a while? That is because wearing them changes the angle of your pelvis and basically pushes out your butt, unnaturally curving your lower spine. It is like you suddenly acquired scoliosis, except front-to-back instead of side-to-side. If you don't know how to compensate for that by tucking your butt muscles or at least properly stretching out your back or whatever, or you can't because you lack the strength in your glutes and your lower back, then you can suffer long-term effects like pelvic inflammation or chronic back pain, especially if it leads to a pinched nerve.
Heels are hot. They are sex on a stick. I really dislike flats and would pick heels over them any day. But you have to be physically able to wear them before you can even consider the implications on fashion and your style. This stuff probably never even occurs to most women, and since even though some of them shouldn't be wearing heels and they do it anyway, they are the ones who end up with shin splints that never heal and broken metatarsals with no idea how they did it. They are the ones who buy Tempurpedic mattresses at 40 to try and fix chronic back pain that they would never believe was caused by some thingies they put on their feet.
If you can wear heels, and if you can find a good style consistent with the shape of your foot, I think heels become a great alternative for anytime. Hell, I wear mine to class sometimes*. The only reason I don't wear them more is because they have buckles and things, which means I can't wake up 20 minutes before class and just slide my feet in and go.
*Campus is a little over a mile away from my house. This means that, why yes! I do walk a mile or three in heels on those days.