You can mix new with old syrup without issue, but not for long term storage. It must be kept cool too, because what you are adding the new to is cold. I suggest you do it, then after basketball has finished, get the whole batch of stored syrup up to 185-190F mix it well, test for density, filter again and pack it in jugs, bottles or SS barrels. If you do that too long after the season you risk losing some quality. Just the reheating will darken it some.
Dave Klish, I recently bought 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.