Almost all the durability difference between shoes comes down to how the upper is attached to the sole, and there are a handful of methods that have been in use for a very long time.
Cemented construction
The upper is glued to the sole. That is the whole method.
It is fast, cheap, allows lightweight and flexible results, and covers the overwhelming majority of footwear produced.
The limitation is repair. Once the sole wears through or the bond fails, replacing it is difficult and frequently uneconomic.
Modern adhesives are genuinely good, so the bond usually outlasts the sole rather than failing first. The shoe is simply finished when the sole is.
Goodyear welted
A strip of leather — the welt — is stitched to the upper and to a rib on the insole. The outsole is then stitched to the welt.
Which means the outsole can be cut away and replaced without disturbing the upper, repeatedly.
The cavity between insole and outsole is filled with cork, which compresses over time to the shape of the foot.
The process is slow, requires specific machinery, and is why this construction sits at a particular price level.
The trade-off is weight and initial stiffness. These shoes take a while to break in and the break-in is real rather than imagined.
Blake stitched
The outsole is stitched directly to the insole and upper, through the inside of the shoe.
Which produces a slimmer, more flexible shoe with a closer sole profile.
Resoling is possible and requires a specific machine that fewer repairers have, and the stitching passes through the interior so water resistance is lower.
It is common in Italian production, where the aesthetic favours a sleeker line.
Moccasin construction
The upper wraps under the foot and the sole is attached to it, rather than the upper being attached to a separate sole unit.
Which produces a very flexible shoe that conforms closely, and a construction that is genuinely different in how it feels underfoot.
Hand-sewn versions exist at high prices, and machine imitations of the visual appearance are widespread.
Vulcanised
The rubber sole is bonded to the upper under heat and pressure, chemically fusing rather than gluing.
This is the construction behind classic canvas trainers and much skate footwear.
It produces a strong flexible bond with good board feel, and it is essentially unrepairable.
Injection moulded
The sole is moulded directly onto the upper, with the material injected around it.
Fast, cheap, waterproof at the join, and entirely permanent.
Most athletic footwear uses variants of this or of cemented construction with moulded midsoles.
What this means practically
A repairable shoe is worth more over time only if you actually repair it, and most people do not.
A pair of welted shoes resoled three times over fifteen years works out cheaper per year than replacing cemented shoes annually. A pair of welted shoes worn twice and left in a cupboard does not.
Which makes the calculation about your own behaviour rather than about the shoes.
The care that actually matters
Shoe trees, used after wearing, absorb moisture and hold the shape while the leather dries. This does more for longevity than polishing.
Rotating between pairs so each has a day to dry does the same thing and matters more than most people expect.
Conditioning leather occasionally prevents cracking. Polishing is mostly cosmetic.
And getting a rubber topy or a heel tip fitted before the sole wears through is far cheaper than a resole and preserves the original sole entirely.
Where I would spend
On the shoes worn most often, which for most people are not the expensive occasion ones.
A well-constructed everyday shoe, resoled when needed, is better value than an infrequently worn welted dress shoe, and it is the reverse of how most people allocate.
The last
The foot-shaped form the shoe is built around, and the single largest determinant of whether it fits.
Every maker uses their own lasts, which is why sizes are not comparable between brands any more than clothing sizes are.
Lasts differ in toe shape, instep height, heel width and overall volume, and two shoes of identical length can feel entirely different.
Which is why finding a maker whose last suits your foot is worth more than any construction detail, and why people become loyal to a brand for reasons they cannot articulate.
Fitting properly
Feet swell during the day, so an afternoon fitting is more representative than a morning one.
Length should leave a small gap beyond the longest toe, which is not always the big toe.
Width is where most fitting problems originate, and many makers offer width fittings that shops do not stock and can order.
Leather stretches across the width and does not stretch in length, which means a shoe that is too short will never be right and one that is slightly tight across the ball may be.