90%

Apparently, 90% of D&D campaigns end at or before 10th level is reached. This statistic does not surprise me at all - I would expect that it has been true right across the editions and applies to Pathfinder as well. Indeed, looking at my own play experience, I'm inclined to think that it is an underestimate if anything. (That said, if you discount 'campaigns' that never get beyond 1st level as outliers, the numbers become significantly tighter... and 90% still feels about right.)

In my own case, I don't have solid recollections of every campaign, or even every campaign that got to 11th level. However, I do know about campaigns that made it into the teens (that being my own, personal, threshold for "high level"). Specifically, there have been three.

The first of these was a Dragonlance/Spelljammer combination, that was also influenced by the 2nd Edition "Legends & Lore" book - and specifically the section on divine ascension. The reason I remember all of this is that the key condition for that ascension was a minimum of 15th level... and therefore that became the entire focus of the campaign. It was also noted that the newly-released Monstrous Compendium featuring not-demons and not-devils (it's complex - the 80s were a strange time) featured a lot of monsters that gave disproportionate XP for their difficulty, and so the entire campaign became one of hacking through endless hordes of these creatures. There's a reason it doesn't feature in my "top campaigns" list... but it does feature in this list as the party did eventually achieve their goal.

The second was the "Shackled City" campaign that I've written about before. At the very end of the session the party reached 19th level. This is both the highest level I've ever gone, and also frustratingly short of the 20th level end-point in the PHB. It was also a strong reminder that 3e definitely broke down once into the teen levels, and so it was as high as I was ever going to go.

And the third and final was the "Eberron Code" campaign, which I've also written about before. That one topped out at 15th level, and was a much more satisfying experience.

My expectation is that the current work game will probably reach 10th or 11th level by the time we conclude "Storm King's Thunder", and that will be the point where we end the campaign. After that we'll be starting over at 1st level, though I'm not currently sure what campaign beckons thereafter. (It will probably be the end of the year before we get to that point anyway, so there's no hurry to make a decision.)

One last thing: the big takeaway from that statistic is something that should be obvious: when planning your character (and indeed your campaign), it's definitely best to go for something that's fun now. There's no real point in planning for what you'll do at 20th level, and certainly no point in deferring any gratification until higher levels, because the likelihood is that you'll never get to that point.

(Also, I'll note that if any of my players aren't enjoying their character, for whatever reason, I'm more than happy for them to make a switch, rather than gutting it out for it to become fun later. I'd much rather you play something you enjoy!)