It's worth remembering that the renal toxicity of Ibuprofen is dose related.
At a dose of 1,200 mg/day the relative risk (RR) of renal failure is 0.94 in the over 65s, at doses of 1,200-2,400 mg/day the RR is 1.85, and at doses over 2,400 mg/day the RR is 2.3.
So the greater the dose the greater the risk. This is why the BNF (British National Formulary) recommends a dose up to 1,200 mg/day for this age group - there will be clinical exception to this of course.