Buy it for Life

3-5 years was what I would get in the army for regularly worn boots. Depends on the sole thickness and rubber type.

The reason that the rich were so rich, Vimes reasoned, was because they managed to spend less money. Take boots, for example. ... A really good pair of leather boots cost fifty dollars. But an affordable pair of boots, which were sort of OK for a season or two and then leaked like hell when the cardboard gave out, cost about ten dollars. ... But the thing was that good boots lasted for years and years. A man who could afford fifty dollars had a pair of boots that'd still be keeping his feet dry in ten years' time, while a poor man who could only afford cheap boots would have spent a hundred dollars on boots in the same time and would still have wet feet.
This was the Captain Samuel Vimes 'Boots' theory of socio-economic unfairness.

There's a pretty big range depending on use and material.

Comments like "x has lasted me y years" don't really help. If they are being used as hiking boots in an area where the trails are dirt/mud/roots, they will last a while. If worn on rough concrete in a job where you walk around in them every day, they will wear fast.

There's also a big difference in the type of sole. Some soles have effectively a big stack of foam as the outsole, which gives you some squish, but wears relatively quickly. Those a generally really thick, though, so it will still take a while to wear through. Some soles are softer rubber so you get better grip, but then they wear more easily. Harder rubbers last longer, but then comfort and grip can suffer.

Dr Martens, and i assume solovair, has one piece of rubber that acts as the outsole and the cushioning. If you wear through the outer layer of the outsole, you can expose one of those air chambers and let water in.

If your gait has you grinding through a portion of the sole prematurely, you could potentially talk to a cobbler about swapping to a different type of sole that won't have that issue.

I used to be a big Keen guy and would buy a new pair of Targhee II's every other year... then it became every year.... the last pair wore out in 6 months. Other hikeresque people have told me Keen is crap since moving production to china - but everything is made in china. I also have friends with different brand preferences who have experienced the same degredation in quality over the years. I honestly have no clue if it's due to regulation with the materials as some have suggested, moving to cheaper materials (the VC special) or what. Long blerb but I am desperate to find a quality brand for hiking that offers a 'wide' option for my sasquatch feet.

Danner boots are top notch and feel broke in from the box. Can't recommend them enough for concrete walking and hard waterproof work days. Their leather and tennis shoe type in sole are quality. You get the slightly raised sole but inside they are flatter unlike a cowboy boot or work boot. They feel like wearing sneakers rather than boots. Top notch!

I bought a pair of keen boots about 5 years ago. I wear them daily from grocery shopping to hours long hikes with my husky.

my soles are prestine. the boot material itself I feel I should have hydrated somehow since the material is cracking on the sides near my toes, but zero issues with the soles.

not sure how or if this helps but it's my experience with keen

edit: I should also mention I walk different from most people. I don't typically walk heel/toe, I put my foot flat on the ground then move forward. this probably also helps my longevity of the soles since I have a much lower chance of scraping it in the ground. I adopted this way because of hiking. ensure solid surface before putting all weight/moving forward, and less chance of tripping on roots and stuff

Folks on r/goodyearwelt and r/nps_solovair have been saying for the past couple years that Solovair's quality has gone downhill. It could just be a vocal minority who have had bad experiences, but that might be the explanation. Because that's a really short amount of time for the soles to wear out on a pair of Solovairs.

Your soles should last way longer than that. On a set of proper boots the soles should last for years and years.

My chelsea boots are from Blundstone, and they show no sign of wear so far. That said I've only had them for half a year or so, so I still consider them new shoes—I expect they'll last many more years.