I can't really advise you specifically, but we recently made the same switch, about 5 years out from retirement. We got started saving/investing very late (I was 29, husband was 39 when he got his first post college career track job), and at that point I wanted the absolute most cash available to invest up front as possible, to make up for our lost decade. This was despite the fact that our earnings early in our investment career were clearly lower than what we were hoping our retirement income would be. So we invested exclusively in 401Ks.
Then as the years went by, and our stache grew and grew, I began to wonder if it wouldn't be better to start paying at least SOME of the tax up front, but of course our income had grown too and it had by that point become less clear that we'd have enough of a stache to put us in a higher tax bracket in retirement, so for about 10 years we invested the bulk in a 401K, and supplemented with Roth IRAs and taxable accounts.
Then, the GOP tax cut bill went through, and it became clear that taxes were unlikely to ever go lower in the rest of our lifetimes (particularly so given that we live in a zero income tax state AND we are hoping to move to an income tax having state in retirement). So despite the fact that moving out of the tax shelter up front would hugely increase our current taxes, it still seems likely that we will have as high or higher a tax bracket in retirement as we do now (with a projected 2 million dollars cash at retirement AND a small pension AND a potential move to higher tax state AND the unlikelihood of federal tax rates remaining as insanely low as they are now), so we have switched to paying most of our taxes up front, not only by investing in Roth401K, but also doing rollovers from the 401K to Roth401K and from regular IRAs to RothIRAs.
I won't lie, the tax bills are ASTONISHINGLY HUGE compared with what we are used to, but I really want to get a big chunk of our stache converted now, so we can lower our tax bracket in retirement despite our projected high annual income. Once we get a big chunk converted, that will leave us more 'tax bracket room' to do conversions after retirement with the remainder. By which I mean that if we have a pension + SS + taxable income from stache, it's likely to put us one bracket higher than if we can draw on pension + SS + tax FREE income from stache. And if we have at least 5 years of tax free income to draw on, we can use whatever 'room' in our lower tax bracket is left over to keep rolling over money as we go along.
