You mention you want a tank with a long storage time. Just curious why that is. I go through Select Sires and they keep my tank topped off at no charge. I think you have to buy a certain amount of semen for the nitrogen to be filled for nothing but I think it's only about 50 straws a year. At any rate I have a MVE Millenium XC-20 tank. According to their chart it has a working time of 125 days with a capacity for 720 straws. I bought mine for $485 a year ago and I see SS has them at $450 in the latest info they sent out.
No specific tank. But in the early spring frequently ABS, Genex and probably others have specials on barely used tanks that have been certified and are as good as new but a whole lot cheaper. They ship tanks loaded with semen to some of the large ranches in the west and AI everything, when they're done they ship them back and check them out. Might be worth checking on.
I was looking for a long holding time because I wouldn't be using it much of the year, and I know friends that have to pay every time a supplier comes around. I forgot about the free fillups. A friend used to dairy farm and I remember he used to get his for free. He didn't know the minimum number of straws you had to buy though to get it free.
A used tank may be the way to go on that. I may have to look into that.
I know select sires does free fillups with so many straws, but does anyone know if Genex does the same? Those are the two suppliers in our area.