I’m in exactly the same boat, and we’re about to do this, by rolling over all of both our existing traditional IRAs ($25k combined) into Roths, and then doing backdoor roth going forward for many years.
To your question of “is this prudent”, I’m pretty sure the answer is a clear yes. I’m not a professional, others should keep me honest if I’m missing something.
The downside is a one-time up-front cost of let’s say $3k penalty from pro rata in the above example. The benefit (vs simply investing an equivalent amount in a standard mutual fund) is avoided capital gains tax on all the growth from up to $14k invested each year (7k limit for each partner). Since we’re not retiring for ~30 years, let’s say investments today will roughly 10x in our lifetimes. So I think the benefits from just the 2024 contribution is ballpark $21k ($140k growth * .15 capital gains tax). And then stacking this benefit for every year of backdoor Roth contributions, the benefit seems to clearly exceed the cost.
