Good call on cutting down on nicotine.
Nicotine is NOT the harmful part of analogs by a long shot. In these doses nicotine is relatively as safe as caffeine.
With that said, if you can comfortably reduce your nicotine intake as you see fit, then I don't see a reason no to.
Yes, the shelf life is a year. I have vaped Halo ejuice over a year after receiving them, with no loss in flavor or potency- If they are properly stored (as chesty noted). Such is the same with many pharmaceutical drugs, which last for many years past their "expiration" date.