Originally Posted by Gunfighter

The in service withdrawal option over 59 1/2 reduces the sting of a low rate of return over a long period. The money is never really "trapped" if you are over the cutoff. Every year removed from the age limit is more lost control of the money. That could be good or bad. I figure mid 50s is a reasonable trade off between loss of long term control and income tax arbitrage opportunity. If you don't have income outside of Delta (ie spouse, business, real estate) the near term tax arbitrage is limited. If you have those external sources, you could draw down the MBCBP in a down year where you take substantial deductions. If you are close to or over the age cutoff, you could take a withdrawal every year with a guaranteed 1.8% ALPA savings.

Another aspect that has yet to be mentioned is the Ultra Mega Back Door Roth IRA (copyright Gunfighter), where you fund the MBCBP with the intention of converting to a Roth IRA. It could be a vehicle for stuffing even more money into Roth accounts, especially if it can be done via in service withdrawal. I'm waiting on plan details before getting too excited about that option.

Opportunity cost is the biggest risk, and that cost is minimized the closer you are to 59 1/2. It is also the toughest risk to quantify.
-Could you miss out on a 10x real estate deal because you had $100,000 invested in MBCBP over the next 5 years?
-Did you pass up on that ecommerce business because you were stuffing an extra $5,000 into retirement accounts the last quarter of the year?
-Did the quest for a tax deferred cash pile rob you of vacations you could have taken with friends and family?
-Are you tracking a Miata when you could have bought a sports car?
or
-Did you save your retirement from bankruptcy when an unexpected event scrambled your personal finances?
-Were you able to withstand the 5 year market downturn that started the day you retired because you had been saving cash for the last decade?