How to find your maximum sustainable spending
The question most people actually bring to a retirement simulator is not “will my plan work?” but “how much can I spend?” Rules of thumb like the 4% rule answer it with one number for everyone. Deorbit Plan’s Strategy Lab answers it for your plan — taxes, Social Security timing, healthcare cliffs and all — by searching for the highest spending that still clears a bar you choose. This article walks through that search, and through what the bar should even be.
First, know what “success” means
Throughout the app, success means the plan never runs out of money before the horizon age — a 90% success rate means the money lasted in 90 of 100 simulated market histories. That target is a dial, not a truth: 99% buys safety in the worst simulated futures by leaving money unspent in almost all of them, while 80% spends more and accepts that roughly one future in five would need a mid-course correction. Real retirees adjust — which is why the Lab has two versions of this tool, one for each spending philosophy.
Step 1 — pick your spending strategy
The solver adapts to the Spending panel’s Strategy selector. Fixed real (today’s $ + inflation) spends the same real amount every year, no matter what markets do — the assumption behind classic safe-withdrawal math. Guardrails (Guyton–Klinger, simplified) cuts or raises spending when the withdrawal rate drifts outside a band. (The third option, %-of-portfolio, isn’t solvable — its floor and ceiling already bound spending directly, and the card explains this if you select it.) The panel’s “Find your max sustainable spending in the Strategy Lab” link jumps straight to the right tool.
Step 2 — fixed real: Tool 1
With fixed-real spending, open Tool 1 — Max sustainable spending, set the Target success slider (70–99%, default 90%), and press Find my max spend. The Lab bisects on annual spending — up to ten full Monte Carlo runs, each probe visible as it lands — until it brackets, to $1,000 precision, the highest spend whose success rate still meets your target. The result reads like “die with ~zero, safely”: the max spend in today’s dollars, the achieved success rate, and — the honest footnote to any success-rate plan — the terminal estate’s 5th/median/95th percentiles, i.e. what’s likely left anyway even at your maximum spend.
Step 3 — guardrails: Tool 1b solves for a floor
Under adaptive spending the depletion question breaks down: guardrails cut spending in bad markets, so paths that would have failed get rescued and the success rate saturates near 100% almost regardless of the starting spend. The risk hasn’t vanished — it has moved into lifestyle cuts. So with guardrails selected, the card becomes Tool 1b — Guardrails floor solve and asks a better question: what is the highest starting spend such that real spending never falls below a floor — default 70% of that starting spend, adjustable — in at least your tolerance share of futures? The result shows the max starting spend, the floor in dollars, the floor-hold probability, and the median lifetime real spending — the quantity guardrails actually maximizes — plus the derived initial withdrawal rate and, for reference, the (near-saturated) depletion success alongside.
Step 4 — sanity checks before you commit
Every Lab result carries two caveats worth reading. The closest cliff approach note reports how near the solved plan comes to an ACA subsidy or IRMAA cliff (warning-colored under $5,000) — a max-spend solution that grazes a cliff is fragile in ways the success rate doesn’t show. And the Lab’s standing banner: winners can flip with market assumptions, so re-run the solve under the historical bootstrap model before trusting the number. When it holds up, Load as Scenario B puts the solved plan next to your current one, and Apply to my plan lists exactly the fields it will change — for the guardrails solve, both the spending amount and the derived initial withdrawal rate, so the strategy doesn’t immediately fight the solved value.
Try it in Deorbit Plan
From the Spending panel, follow the “Find your max sustainable spending” link to the Strategy Lab. Run Tool 1 with a Target success of 90%, then switch the spending strategy to Guardrails and run Tool 1b with a 70% floor — comparing the two max spends shows what spending flexibility is worth in your own plan.
Educational content only — not financial, tax, or investment advice.
See how this plays out with your own numbers. Try it in the simulator →