Herbs do loose potency through time. And the way you store them makes a huge difference. You should avoid heat, and light and they should be stored in clean containers. Cool, dark storage will help preserve their shelf life.
Ideally you want to use dried herbs within a year since you’ve sourced them. But they will last beyond that. If you notice the color has begun to fade and their smell is less vital, add extra to your tea and infusion.
Powdered herbs should be used as soon as you have them. Source them in small quantities and more frequently. At max, try to use within 6-12 months.
Liquid extracts are a different story. Tinctures will last much longer, as they are preserved, often with alcohol. Alcohol based tinctures are good for years, though may loose potency by 4-6 years. Most herbalists say vinegar extracts should be used in 6-8 months, but if stored well it can last longer. Glycerine based extracts should be used within a year or 2.
Herbal honeys last about a year.
These are general guidelines. You can use your senses to gauge how much vitality is in what you’re storing. Notice its color, aroma and taste. For dried herbs see how it feels between your fingers. Is that different than when you first sourced it? You can also notice if you need more for the same effect, which may just mean it’s lost some potency.
