One recipe, or litmus-test, or whatever moniker we use for making a decision, is to assess annual contributions from salary, vs. extant portfolio. Your portfolio is now around $1M, and your annual contributions are about a quarter of that... ratio of 4:1. That's an enormously powerful incentive to keep working and saving.I just hit the million dollar milestone, .... We tuck away about $12k per month to retirement/investment accounts. ...
Assuming a decent stock market, consistent savings-habits and no enormous increases in salary, you can use your favorite calculators to estimate portfolio-to-savings ratio as the years advance. More common is to use a safe withdrawal ratio or ratio of annual expenses to portfolio, but this doesn't account for opportunity cost. The current suggestion does.
At some point, you might have a ratio of portfolio to annual savings, of say 40... ten times more than currently. Is that "enough"? Subjective, of course! But we can intuit that a 4:1 ratio means a large opportunity cost (not that you'd consider retiring today), whereas 40:1, vastly less so. Pick a ratio that appeals to you, and use that as a criterion.