Based on Kenneth French's yearly Small Cap Value (SCV) data since 1927, combined with Robert Shiller's One Year Interest Rate and CPI data, I ran a backtest to see how many years it took a 50-50 SCV/One Year Interest rate yearly rebalanced target asset allocation to grow $40 to $100 in real terms.
Average 10.95 years
Worst 17 years
If an investor deposited $60 into inflation bonds with the intent to draw down those funds over 20 years at $3 inflation adjusted each year, the historic indications are that the $40 in the above growth asset allocation would have replenished $100+ in real terms before those income/drawdown funds were run dry.
Drawing down one bucket (income) and allowing a growth bucket to expand (replenish) has the effect of cost averaging more exposure over time (start with 20% of total allocation to SCV, and maybe end up with 50% SCV weighting). The general indication of profit taking surplus gains out of growth etc. indicate around 30-70 average SCV/One Year Interest rate average weightings for such a 2 bucket approach and as such might be compared to a more consistent single bucket 30-70 approach, and the comparisons of those indicate somewhat similar overall results (rewards).
If the two bucket and single bucket approaches provide somewhat similar overall reward, then I'd suggest that the two bucket is potentially the safer overall choice. With the two buckets you cost average into SCV more progressively. When the initial 60% income bucket is invested in safe inflation bonds the 20 year of 3% income provision is also safer/more assured. The single bucket approach runs with a greater risk of potentially feeding a bear, that when combined with income withdrawals could result in insufficient income being available before the end of the 20 year horizon should an out of sample bad period be encountered. With the two-bucket approach the income for 20 years is kept separate.
That potentially moves risk from yourself to your heirs. For example assuming a 65 year old at the start date, then you'd have 3% yearly income to age 85 - and only if you survived to beyond that age would the performance of the growth part become a concern. In the average case the growth funds might be periodically profit taken in order to supplement the 3% core income and still potentially leave an inheritance comparable to the inflation adjusted total original amount of funds (or be available to reiterate in the event of longevity).
Asymmetric based management that avoids moving funds intended to maintain core living expenses towards potentially feeding a bear is a more protective measure, whilst broadly still achieving similar rewards when managing the portfolio that way compared to the single bucket approach.