The earth's economy has proven a lot of doomsayers wrong during the decades, but the general idea of planning with a slightly larger margin of safety kinda makes sense to me.
Thoughts?
I'd advise a low information diet. If you read enough gloom and doom BS you might start believing it.
To your point of more safety margin I'd reply as long as you are not conflating safety with simply accumulating more money I can agree.
Being flexible with your spending to adjust to poor return years does wonders for your portfolio's longterm health and doesn't have to hurt a ton as long as you aren't planning for a beans and rice retirement in the first place.
Add in some limited part-time work options if you need to limit your withdrawals for a while and you've got a pretty powerful safety net that doesn't requires years more of your precious life to accumulate money and only need to come into play if the gloom and doom stuff comes true. Having a part-time work option or a 25% reduced budget option does not mean you'll ever need to use it. It's just an insurance policy and one you don't need to pre-pay.
OTOH if you are only looking at more money as your safety plan I think that's a poor choice.
http://www.mrmoneymustache.com/2012/01/13/the-shockingly-simple-math-behind-early-retirement/- assuming your want $40K/yr in retirement and start from zero with a net $80K salary and a 50% savings rate
- Good old Mr. MM's chart tells you that you'll need to work 17yrs to accumulate $1M for a 4% SWR
- now say you figure I better actually to save for a 3% WR just to be safe
- at 5% return after inflation that's an extra ~3.5yrs to get the extra safety margin
- if you are even more conservative than that and want a 2% WR that's an extra ~9yrs
To me the opportunity cost of working an extra 3.5 - 9yrs full-time during the prime of my life is not a sensible trade off for dealing with the potential that the already quite conservative 4% SWR fails. Especially when you consider there are many ways for your FIRE to fail that do not involve money.
If your health or the health of a family member suddenly takes a turn for the worse a 2% WR is not going to be of much use to you. OTOH having an extra 3.5 - 9yrs of free time to spend with them before that happens is priceless.
I know these non-cost factors get overlooked on MMM because there is no Excel function for quality time with loved ones, but personally that risk is a far bigger concern to me then the 4% SWR failing and my not having any way to respond to the problem.
Retire CanadaEmperor of Positivity
Lord of Flexibility