Badass savings rate, good job.
You can stop contributions if something happens to a property and you need a little more cash in a given time. It's rare that 1. The roof blows off and 2. It isn't covered by insurance and 3. The tenant withholds rent and 4. The guy fixing it for you won't accept a payment plan and 5. The bank you have a relationship with won't lend and 6. It happens again at your other property the same week and 7. all of this happens at once. If it does happen, stopping your contribution entirely and dumping the next larger paycheck on the problem ought to go a long way.
Part of it depends on the investment vehicles allowed within the 401k. My last job the 401k sucked, so the only "return" I could expect was the match + the tax savings.
Assuming they are worthwhile:
Break down your scenarios, more into the 401k vs, current vs. less.
Figure out the actual taxable income for both scenarios using likely deductions and the best estimates/real data you can.
You end up with a difference in taxes between the two scenarios, that difference is the relevant factor. Compare that to what you think you could be earning investing the money outside the 401k (in your case, real estate). You can also try to factor in returns on the value of the real estate+rent-expenses vs. the investment vehicle of choice in the 401k, but I don't know a great way to do that, as I can't predict any of those markets.
Also, I think if you go into real estate as an agent it changes the tax situation on rental property you own. I don't know if that is advantageous, but it probably factors in to the long term strategy. There's something fuzzy buzzing around the back of my head about this.
You also have a tIRA as an option in lieu of the 401k, if you would like more options in your pre-tax savings.
Take a look at your draw-down strategy as well. How you intend to access the accounts will affect where you put your money.
If your version of FIRE is managing a bunch of properties and living off of that income, then you may not need to be saving money where you can't use it to reach the right number of properties for you. Having income from those properties may be enough such that a tax-deferred savings doesn't make sense (your long-term income stream from sources-not-retirement-accounts will not be significantly different than what you've got now).
In the back of my mind has been this idea that I could take the savings I have now, buy 4 or 5 decent properties, rent them out, and quit my job. But I'm suspicious that managing them would be similar to working, probably more satisfying, but ultimately less lucrative. It isn't really an option though as most of my savings is in retirement accounts. It takes me a loooong time to save up enough for a downpayment outside of maxing my RAs.
So I guess for me it was a choice between two scenarios, and I went with going the tIRA/403b/457b route, and once there's a huge pile of cash there I may go ahead and pick up a property. I couldn't do both though.
Good luck!
