Yes, old lentils can take longer to cook. This is because older lentils, especially those that have been stored for long periods of time in dry conditions, may suffer from a lack of moisture which can inhibit their ability to soften during cooking. Additionally, some trace minerals and nutrients that are important for taste and texture may have leached out over time as well. To ensure faster cooking times with your lentils it’s best to buy fresher varieties if possible and store them at recommended room temperatures or slightly below (20-25 degrees Celsius). Using a pressure cooker is also an effective way to reduce the cooking times of your older beans as it will force more heat into the plant cell walls which breaks down tougher fibers more quickly so they cook faster.