This is different for everyone. The ready made blends such as the Help Blend and Slow Down Blend can have an immediate effect as well as longer lasting effects. Personal blends can be felt immediately or may take a few days for you to notice changes. Some people notice a difference after a couple of weeks and some notice when the blend has been completed as they feel different once stopping them (which often means a refill is probably needed).
The more often you are your blend/s, the greater affect they will have as each time you take them, you are 'topping up' the essences frequency in the body which allows them to have a longer lasting and stronger affect.