The best practice for your own retirement planning is not to use inflation as a basis for withdrawals or modeling your withdrawals. That's why you focus on your own individual expenses which are going to reflect any inflation that applies to you and then plan based on that. Another way of thinking about this is if you believe somebody's projection that for whatever reason portfolio returns are going to be 20% less in the future than they have in the past, that is already accounted for by using a more realistic assumption.