This is NOT a simple question. The 'When' has to do with financial capability, as well as mental aspect, and certainly health. Keep forgetting that not everyone has a financial mind. Read too many "How to retire on $1 million" stories. Not sure that even with a free and clear home, one can live on $4,000 per month, and not eat ramen every night. But key for me was, Do you enjoy your job? Do you have your health? Do you have the money/investments/retirement (beyond SS) to live comfortably. Would also add, will you suffer a loss in standard of living if you retire? Key to financial/wifey happiness. Biggest cost of retirement is health benefits. And yeah, the increase exceeds any inflation out there, certainly that of income increases. First thing is to secure H&W benefits, see if your company offers retiree benefits, and sign up for those. If they know, find out what increases have been, as being on a 'fixed income' you'll have to absorb those increases from your income stream. Next, pin down your sources of future income. By now, everyone is looking in the rearview mirror, and saying "wish I woulda saved more" etc. When I retired, took out enough from IRA to cover the costs of H&W, so didn't suffer any loss in standard of living. Maybe rearrange your portfolio to generate income instead of gains. Changed my 'reinvest' in portfolio earnings to move to cash account to provide some 'extra' funds for cruises/vacations etc. Maybe you work several more years, and make a concerted effort to stash money away in 401(k), Roth, etc. Pay off as many debts as possible.
Will stop, as never can ascertain whether the questions are rhetorical or just meant to entice responses. But no matter how much you plan, there's always some variables that you have not taken into account, or some twists of fate unknown at the time. Good luck.