Hair shampoos are a really good product to maintain healthy hair. You should not change your shampoo as long as you are getting the intended result.
However, if you feel you have achieved your result from the shampoo and want another result, maybe a shampoo for thick hair or full hair, you can change your shampoo.
Whenever you want to change your shampoo, make sure you check the component of the shampoo so you won’t damage your hair.
Do not change your shampoo every time. However, if there is an upgrade or a better version of your shampoo, you can still use that. If you are not getting your intended result, you can as well change your shampoo.
One of the problems being encountered by a lot of people, especially women, is that they really don't know the right shampoo for their hair, and how often they need to be changing it. In my opinion, I do not think you still need to go for a change once your shampoo is giving you the intended result. Changing it just because another new product is being gotten by your friends, or just because someone recommends it for you might not always be the best decision for the healthy maintenance of your hair.
Also, the current changes you are noticing about your hair might be influencing your decision to change your shampoo, but it will interest you to know that there are other factors that could be causing the changes. Invariably, I will only advise you to change your shampoo once you are not okay with the end result of its reaction with your hair.