@sol, would you be willing to share how you did all that
There is no template, sorry. But I can describe it to you.
In excel, I made a column of every sequential month between retirement and death (in my case planning on age 100).
In the next columns over I made my age and my partner's age in that month.
In the next column over I put my checking account balance in that month.
In the next column over I put my estimated expenses in that month (adjusted up for inflation each month, and including my mortgage changes and then eventually empty nesting).
Then in the next columns I put the forecast balances in each of my retirement accounts, with an adjustable return rate so I can test what happens at 0% vs 10% market performance. I keep separate columns for the estimated future value of my rental properties (90% of equity to account for sale costs) .
Each month, my checking account balance goes down by my expenses from the previous month, and up by the amount of any regular income I have (rent surplus, solar panel payments, etc). When the checking account gets too low, I take money out of one of the investment or retirement accounts by depleting the investment account and adding that amount (minus taxes if applicable) to the checking account column. First I draw from my taxable account, because it is restriction free. Then I draw from my Roth IRA principal contributions, since those are also restriction free, then Roth IRA interest at age 59.5. At age 60 my wife has a pension, which I add to my checking account balance each month. My pension starts at age 62. Then social security. Our expenses go down a little when the kids move out, and a lot when our mortgage gets paid off. If I have to draw from my 401k plan early, I play on paying the 10% penalty in addition to regular income taxes on that amount.
I graph our net worth over time from all sources under various scenarios, like 0% stock market returns and 5% inflation vs 8% returns and 2% inflation. I can mathematically "sell" a house if necessary, removing it's monthly rent but pocketing the big check from the sale, and the future house value is adjustable (currently assuming 1.5% per year appreciation).
It's not a stochastic model, so it ignores market volatility. If the market goes down 25% in one year, I'll have to manually update the spreadsheet's account balances but presumably it won't continue to go down 25% every year.
Then I've added some additional complications, like making annual Roth IRA pipeline rollovers and how to minimize our paper income for ACA subsidies or FAFSA applications during the relevant year by only withdrawing from taxable accounts during that window.
Basically, the whole thing is designed to give me a roadmap. There are notes in the far right column of important dates, like SS eligibility or Roth IRA rollover maturation dates. I should be able to just follow along over the years, updating balances as necessary, and always have a pretty clear view of what our financial future should look like. If the future gets ugly, the spreadsheet should make it clear that it's time to adjust the plan or even (gasp!) go find more income somewhere.