It's one of the features of Ibuprofen that you can take it at those levels without killing yourself. Most people don't, but some people do - sometimes because doctors tell them to.
This makes it different to Paracetamol, where you only have to double or triple the standard dose to cause temporary liver damage, and increasing it only slightly further puts you in danger of death.
> it's not a dose people will commonly take in their "day to day" activities
A lot of people who exercise multiple times a week take "Vitamin I" every day. So do people who have frequent headaches, back or joint pain, etc. I probably came close to these levels during a bout of plantar fasciitis, though I've since switched to naproxen in such cases. It might not be common in your immediate circle, but in the broader world it's not rare enough to raise any eyebrows.
I went through a period of heavy physical activity without good equipment, which caused quite bad shin splints. My doctor prescribed precisely this dose, along with some physiotherapy. I think it's quite common for inflammatory problems like that.
Wow, all the ones I have (and I don't remember seeing any different in Australia) all say do not take for more than three days at a time (except with a doctor's advice).
Are you sure it didn't have codine in it? In the UK, the only (AFAIK) non-prescription medication with that sort of warning is anything containing codine.
Correct. Adults can take up to 800mg q6hrs and I routinely prescribe that dosing after ankle sprains, etc for a few days. 6 wks duration would be way out of my comfort zone.
But it's not a dose people will commonly take in their "day to day" activities and ideally not something that is done without medical supervision