That’s totally up to you. My personal number is about 5-10 years from retirement, though I’m pretty risk tolerant.
My plan is a rising equity glidepath. Basically, I’m going to load up on bonds (20-40% bond tent) a few years before retirement, and then ramp back down to no bonds in the first 10-20 years of retirement. I’m planning to retire early, and this plan seems to have a higher chance of success vs a consistent bond portfolio given a >30 year retirement.
The same strategy works for a shorter retirement, and you can keep your bond allocation constant as well. This strategy makes sense if you have a high risk tolerance, but recognize the need for portfolio stability in retirement. If you have a lower risk tolerance, do the “normal” strategy that target date funds use: 10% starting out, and increase as you get older.