Based on the original Agefix recipe this fixer is more complex in it´s formulation than the standard ADOFIX. Especially the buffering system contains more substances which makes ADOFIX Plus last longer in the open tray and gives it a bit of extra capacity.
General recomendations for liquid fixers: Liquid fixers stay fresh if kept unopened for about 2 years.
After opening the concentrate shall be used up within about 3 months.
I case of flockulation or sulfuric fumes the fixer cannot be used anymore.