A link to the rebalancing spreadsheet may be found on this web page. Look for the green DOWNLOAD button in the Downloads/Resources section of this web page above and click on it.  You'll then have to click on the download arrow in the upper right.  Once the spreadsheet is opened, go to the Start tab in the lower left corner and then choose the right version of the WMB portfolio.

NAV stands for net asset value.  It is the liquidation value of an account, sometimes referred to as the equity level of the account.

Time horizon is a critical factor to consider because of the severity of bear markets and the number of years it may take to recoup losses following darker periods in the stock market.  If an individual has, say, 10 years remaining in his lifetime, that may not be enough time to recoup losses - which is a serious threat for seniors who are over-exposed to stocks.

First, choose the right version of the WMB program (Emerald, Standard, Silver or Leveraged).  Next, update the NAV in the upper left area of the spreadsheet.  This cell has a light blue/cyan background.  You'll also need to update the exact number of shares of each fund (ETF or mutual fund) that you currently own on the right-hand side of the spreadsheet.  These cells also have a light blue/cyan background.  The spreadsheet automatically updates the latest prices of each fund, and will tell you exactly how many shares you'll need to either buy or sell (under the Adjustments column, which appears in red font).  

You should rebalance your WMB portfolio once per year - no more, no less.  Studies and backtesting show that this is the optimal frequency for rebalancing.  I suggest that the best time to rebalance your WMB portfolio is the second to last week of December, prior to the Christmas holiday.

No. Rebalancing should be done annually in December by all investors - seniors as well as younger investors who are still making contributions to their Roth IRA or 401K (or taxable accounts).  Monthly withdrawals should only be made by seniors during retirement to help pay for monthly living expenses, and/or to meet RMD requirements.  The upcoming video shows you how seniors can make monthly withdrawals from their WMB account at Fidelity. 

For seniors, I recommend using Fidelity because of the automatic rebalancing program, which comes in handy during retirement when you're making monthly withdrawals or taking RMDs.  For younger and middle-aged investors, I recommend either Schwab or Fidelity.  Leveraged versions of WMB (for institutional or high net worth investors), should be run at Interactive Brokers.