Once FIRED, the value of bonds is in part the ability to sell something with a fixed value during downturns instead of equities. Therefore, I'd say make sure that they are in your taxable as you approach FIRE assuming you won't be over 65 at FIRE.
I wouldn't worry that putting bonds where they are going to get the best tax treatment (in a retirement account) would create problems during retirement. Remember that dollars are fungible.
If the market is down a lot and you want to sell bonds to cover living expenses but your bond allocation is entirely in 401k/IRA investment space and your taxable investments are all in stocks just:
1) sell the amount of bonds you want to withdraw inside your retirement account.
2) sell an equivalent amount of stocks outside your retirement account.
3) use the proceeds of step #1 to buy stocks inside your retirement account.
Viola, you've sold bonds, have net zero change in your stock investments, and didn't need to take on extra tax liability to be able to do so (it just took two extra clicks on your computer).
mntnmn117: To the extent possible hold bonds in your tax preferred space (401k/IRA) so that you can avoid the higher income tax rates on bond interest vs dividends and international stocks in taxable space so you can benefit from the foreign tax credit on the automatic tax withholding of foreign dividends. Domestic stocks can go in either.
If you're rebalancing because one part of your portfolio has increasing in value faster than another it's better to do that in a tax preferred account (to avoid capital gains) and if you're rebalancing become one part of your portfolio has declined in value slower than another it is better to do that in a taxable account (to harvest capital losses).