For me, at least, there's no "race" from 2-4 million in the way that there was earlier in the FIRE process. Thirty years ago, saving to invest made a difference in my financial trajectory. Today, all I really have to do is watch compound interest do its thing.
At this point, the earnings on my investments are far more significant to overall growth than contributions. The time it takes to double will be almost entirely dependent on market growth. If the S&P 500 averages 10 percent growth, it'll take about 7 years. If it grows at 7 percent, it'll take ten years.
It takes some of the fun out of things, but it is a good position to be in.