In the past it might've made sense for some people to "double shield," meaning they also shield their OA balances just before their 55th birthdays. That'd mean their new RA gets funded to $60,000 ($40,000 from SA, $20,000 from OA), and then they'd quickly make a large cash top up to RA to get it up at least to the Full Retirement Sum (and "liquify" their SA and OA but keep those dollars parked for a while). However, given that even ordinary 6 month T-bills are yielding more than OA it's probably not a great idea to shield OA any more. I suppose it depends on your interest rate forecast. You might forecast that OA's 2.5% floor rate will be attractive enough again fairly soon, and for some time. It's up to you, of course.