The hamstrings are in a connected line of pull from the pelvis via the sacrotuberous ligament structure to the sacrum, up the back extensor muscles all the way over the skull to the eyebrows. Also in the opposite direction, the hamstrings are part of a line of pull that connects down to the plantar surface of the feet. The hamstrings and muscles of the back body create a line of pull that keeps us upright and the tension in the back keeps the shock absorbing curves strung.
If you store them in air-tight bottles that are not opened day-in day-out, you can expect your e-juice to last anywhere from 12 to 24 months. However, there are other factors in play like the purity of the nicotine used, the quality of the flavoring and the manufacturing process.
Gas loses its potency over time and this also applies to Diesel and Kerosene. Diesel for example if stored at lower than 70 degrees will last about 12 months without any additives provided it is kept in a sealed container. If your temperatures are much above 70 that time slips by 50% to 6 months.