Fisrt define whether you are testing continued use of opened containers, or fresh constiners. Note also that shelf life data applies to specific methods, so choose those where the experiments will provide benefit. You need your quality people to sign off on the protocols before you start.
Simplest method is to make up a large amount of mobile phase, store in typical containers, and use them to analyse standards and/or samples alongside fresh mobile phase, preferably from the same batches of components that will not exceed manuafcture's expiry date during the trial ( apart from water ), in a time sequence relevant to how long you would normally use them. eg 1 day, 1 week, 2 weeks, 4 weeks, 3 months, 6 months, 1 year, etc.... You method quality data will tell you if results are acceptable.
Note that some components will have shelf lives determined by other factors, such as potential wildlife growth in biologically-benign fluids, eg pure aqueous, aqueous + buffers - typically 1 week maximum, unless you take extra precautions. Other time-limiting factors are moisture ingress ( hydroscropic solvents ) or stability ( ethers forming peroxides ), etc. etc. Don't waste time trying to entend those.
Organic components should last at least 6 months, if not to manufacter's expiry, and most mobile phases will have shelf lives somewhere in between pure aqueous and pure solvent.
Good luck,
Bruce Hamilton
