I'm not sure how to respond. Weather affects vacuum, so not sure where you got the impression it doesn't. You suggesting there is less syrup now than 20 yrs ago?
2017: added shut-off valves at several points on the main line, 66L made, 13L sold
2016: Added Wesfab 7" Filter Press with hand pump, 96L sold
2015: now 216 taps, added low vac (24" hg) to new Sugar Shack (24' x 16') w/400gal storage, 143.15L sold
2014: now 150 taps, added 2 sump pumps to 12'x12' sugar shack w/100gal storage to CDL 18"x5', 2 chamber drop flue, 40L sold
2013: 10 5/16 taps gravity to hose, boiled on BBQ