I was begining to think I was going nuts, and completely ruined one maybe two pairs of boots in the process, until I talked to a cobbler. Read on to find out more...
My feet legitimately have grown a half a size sometime in the last decade. That resulted in having to turn over some boots I was pretty satisfied with. In addition, I've been experimenting with different weights and types of boots to try to optimize for efficiency. It's kind of my job. And I'm kind of a boot whore. So I've been been through some boots in the last couple of years.
About a year and a half ago, I got into some Garmonts I was very happy with. Then I oiled them and had what I thought was an internal glued leather seam separate so that it protruded painfully into the toe box. I chalked it up to a model specific issue. Since I'd gotten such a deal on them (< $150 for a legit pair of backcountry boots) and liked them so much, I already had another pair on the shelf that I hadn't planned to break out for at least 5 years. I pulled them off the shelf and put them into service. After 3 or so months of good use, I started feeling like they were a little too short (guess I'd called sizing wrong) and also I wanted more support if possible.
So I got a pair of Kaylands that I was (am) absolutely in love with. After 3 or so months of good use, I started feeling like they were a little too short (guess I'd called sizing wrong), so I got the next half size up. They had plenty of space in the toe box but didn't feel clumsy. Problem solved. Until I oiled and sno sealed the larger ones for the first time (less than a week old). The next time I put them on, there was a painful ridge inside the toe box protruding a full half an inch into the side of my toe. Bear in mind I put in boot trees after I oiled them.
I immediately took them to the old school cobbler in town. As soon as he felt the ridge, he said "Yeah, I've been seeing that a lot lately. Some kind of synthetic internal stiffener that they're putting in boots now. As soon as it gets a wrinkle in it, the boot is done. I've tried everything - heating and stretching, hammering - there's not a thing I can do to correct it." Lightbulb moment - I went back and put thinner less supportive insoles into the boots that I'd "called sizing wrong" on. Both of them were plenty long, the problem was that the inside of the toe box had curled and shrunk downwards over time and use which effectively made the boots too short with the insoles I'd originally sized them in.
I'm not entirely sure what course of action to recommend to folks regarding this issue. I've been using exactly the same prescription for boots since 1993 - White's boot oil to condition the leather, sno-seal to waterproof and protect it. I've never had this problem before the last couple of years, and that prescription has always worked flawlessly to keep boots in good shape and also water and scuff proof. At the very least, I'm going to be super cautious about treating boots going forward. It rubs me the wrong way not to care for a good pair of leather boots, but maybe you can't oil boots anymore. Functionally, you do want sno-seal on goretex leather boots because even if your foot doesn't get wet, you still don't want the leather to absorb a bunch of moisture. Maybe sno-seal is OK. In talking to the cobbler, it didn't sound like the problems he had seen were necessarily caused by oiling boots. Sometimes it was just because the boots got wet, sometimes it was just use.
Maybe you only get synthetic boots (since it's not a good idea to oil boots anymore), but there's nothing to say that synthetic boots don't have the same stiffeners. In fact, it seems more likely to me that synthetic boots DO have the new synthetic stiffeners which will curl inwards with time and use.
I went and re-read product descriptions, and couldn't find anybody bragging about putting special toe caps on the inside of their boots, so there's not really a way to know upfront if a pair of boots you're looking at has them. Maybe it's just the Garmonts and Kaylands (which do look pretty similar in design and construction), or maybe it's all boots of that type (heavy backpacking / light mountaineering) that are made in Europe.
On a personal level, I've regained the use of a couple pairs of boots I thought were done -- so long as I use thinner insoles. Maybe the thinner insoles will end up being fine for my uses. Don't know -- I've been using the thicker ones for a decade now. I also think I've managed to repair the new half size bigger boots with the use of a heat gun and inflating a bicycle innertube inside of the toe box and letting things set. Or maybe a handful of miles on the trail will make that wrinkle pop right back into the toe box. Or the next time I walk in wet snow.
Consider this a heads up - at the very least, don't be in any kind of a hurry to oil your boots. Even though decades of experience indicates just the opposite.