Once or twice per year, as-needed, I replenish one or both of our cash accounts to their target levels. If I sell something in that process, I'll immediately rebalance as necessary. We have pensions, rentals, and dividends that cover basic living expenses. So this replenish/rebalance process generally only happens in conjunction with a major expenditure (new car, home improvement, international travel).
Twice per year, I have a phone call with our Fidelity Private Client Group advisor. Nothing much comes from this. We walk through the latest RIP numbers, and she'll make a suggestion or two about the portfolio, which is usually pretty good.
At the end of each month, I login to Personal Capital and let it accumulate all balances and transactions. I usually have to update or correct the account category on a handful of credit card transactions. I look for anything unusual or unexpected and discuss with DW. I then spend a few minutes looking over the AA, performance vs benchmark, yield, and other portfolio analytics. I then transfer summary amounts from Personal Capital to my retirement planning spreadsheet... (1) month-end values for each holding, and (2) monthly spending by account category. Again, I spend a few minutes looking at AA, yield, performance, etc; and also compare spending to our budget by category. Periodically, I work on the withdrawal strategy tab as well, usually as it relates to SS timing and potential Roth conversions, which I'm still trying to optimize.
Once per quarter, I update the tax planning spreadsheet with the estimate for the year and send a payment to the IRS if needed. There's a tax tab in the retirement spreadsheet as well for projecting tax many years into the future. So if anything significant has changed in the current year, I'll update the baseline there as well. In December, I update this with the latest distribution estimates and other data to firm things up as much as possible. I'll also evaluate tax loss harvest opportunities, Roth conversion, make an HSA contribution, decide when to pay property tax and charitable contributions, etc.
That's about it. From time to time, I rethink some aspect of the portfolio. Like right now, I'm slowly reducing the cash allocation, increasing international equity, and replacing long-duration bond funds with a stable value fund. I'm also still researching two big ER topics which I'm undecided about: (1) SS timing strategy for DW and myself; and (2) Roth conversion strategy. I always read anything on this forum and elsewhere related to those topics, which is quite helpful.