Hello,
all Anilin-based colours fade within several years of exposure to bright sunlight,but this is certainly not the thing going to happen to Your ink bottle....
Most manufactorers recommend to use up their ink anyway within 1 year because of the relative instabilitiy of detergents used,5 years should be alright too,but then better get a new bottle.
Document proof inks(many black and blue-black ones) contain certain amounts of drawing ink,a problem for many pens,but it gives them almost perfect colour-durability to sunlight.
In Your case,You need bot bother.
regards,
lutz