Years ago, our workplace Fidelity rep said they were now using "120 minus age = bond percentage" to deal with the fact that people were living longer.
I ignored that advice until I hit 50, as our risk tolerance is high - I have a well-funded pension coming to me, we have underestimated Social Security benefits in case of a cut, and we do not account for any inheritance.
Once I hit 50, preservation became more important. In the last year, we've rebalanced - as well as included another employment account that is essentially an annuity as part of our calcs. It puts us at 68/32, and I find myself unwilling to go higher.
So, at 54 (and six years out from our planned retirement date), we're pretty spot on to the "120 minus age" formula. YMMV.