Key ages and smooth withdrawals
For the benefit of others, I'll share an approach I just devised that seems to work well for me. Instead of assuming smooth withdrawal over my lifetime with an expected age of 100, I'm setting my smooth withdrawal end date to the year I'm 71. That's the year after I start withdrawing SS.
This works for me because my wife and I have retirement accounts of approximately equal value, she's a few years younger than me, and will continue working 3 years after I retire. In the current scenario, that's early 2018 for me and early 2021 for her.
If I set the last year of withdrawals at age 100, the value of the smooth withdrawals is far too low to provide for our needs in the years between my retirement, and my starting SS. An important fact is that we're very constrained as to regular assets, but I think that's typical of a lot of people.
Anyway, by setting my last year as 71, all of my retirement accounts are exhausted at that point but the higher withdrawal rate supports us until SS kicks in. My wife will start drawing SS at retirement at 62, at which point I also get my spouse benefit. We'll draft her retirement accounts smoothly over her lifespan.
So, my point is, if you have a spouse/partner with retirement accounts you can rely on, consider shortening the smooth withdrawal period for one or the other. It made my plan much easier to manage. Without that I had to use special withdrawals for the first 7 years and, as others have described, had to play whack-a-mole to avoid hitting 0 on real assets.
I hope others find this useful.