Lynn, the fluorochromes are not the problem, they are pretty stable, as long as you don't expose them to direct sunlight. I'd be more concerned about the dilution, as, when no carriers (serum, BSA, etc) and detergents (Tween 20, TX100, etc.) should be present, your antibodies happily will disappear over time by adsorption to the container's surfaces. You also might want to add an anti-microbial preservative (0.09% NaN3 will do).

Wolfgang Schechinger If it helps, I do not dilute my antibodies when I make the cocktail, they are in the same suspension as the original tube, just mixed.

Our lab-made FACs buffer contains sodium azide and BSA, would it be better resuspended in the buffer or as it is right now?

No panic, gently treated, antibodies are quite robust fellows.

If you just mixed aliquots from the original vials, no worries. Keeping proteins as concentrated as possible will maintain their stability.

If you need to keep them in the fridge for a longer time, and they don't have a preservative added (check the datasheet or ask tech service), add a little sodium azide (from 10% stock, dilute to 0.5 to 1% final), as they might not be sterile anymore.

If you need to keep them longer than a week or two and if they should have arrived with a substantial amount of glycerol added *and* were previously frozen, better freeze them again (flash freeze in liquid nitrogen if possible, then store at at -20 or lower), maybe in aliquots.