If in doubt, keep the latest sap separate until you test boil it. Bad sap will smell like dirty socks.
The type of trees will vary greatly when you should quit. Sugar maples have pointed buds early on, as the season nears the end they will swell, then at the very tip a little color will appear, they are done then. On Red maples the sap will stop flowing before you need to quit, on silver maples the buds, which are large flat top clusters will open and flower, (reds also have very similar buds). Once any color appears on the buds, time is over. Both Reds and silvers will be over a week and maybe even more than 2 weeks before sugar maples are done. The timing does not use a calendar, it's all related to the weather.
Here in central NY I've been done some years as early as March 22, and as late as April 24. Every year is different.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.