The best place to store nicotine long term is in the freezer. I store mine in the refrigerator. It won't freeze in the freezer but it does thicken and then you have to wait for it to warm up a bit before mixing. You really need to keep it away from heat and sunshine. Heat and sunshine will speed up the oxidation process and it will start to turn amber and darken as it ages. It is crystal clear when purchased and will stay that way for a LONG time if kept in the freezer. You probably could just keep it in a drawer if you plan on using it all in a few months.
There really isn't a firm expiration date on nicotine. Some people (Chemists) on the ECF say it should last at least 2 years in the freezer, maybe even 5 to 7 years, but nobody really knows.
Good luck!
Pete