Most of the new ones are pretty dang efficient, especially for beef cattle operations where you aren't opening it as much as dairy. We have an MVE XC20 and it hasn't been filled except for the first time and its been over a year.
Had the same tank years ago when we milked cows and if I remember right it hardly ever needed nitrogen added.
our semen tank hardly gets even opened this time of year and our nitrogen supplier truck still shows up about every 12 weeks to top it off usually takes about 11 liters of nitrogen. we have the MVE Millennium 2000 XC20 tank.
with the value of the semen and embryos in my tank and im sure other peoples tanks, i would never ever go a year without filling it even if it could last that long. ill pay the 30 dollars every 3 months to have it filled... i would hate to check it one day and its empty...
