I've changed my profile picture twice I think. Considering it again. I've been doing this for 5 years and I believe my first profile picture (similar to this one) was my go to for about 2-3 years. Then I wanted a crisper more professional look, so I vectorised my display pic and I've been using it for maybe 2-3 years. The idea is for people to recognise you, and if you keep changing your display picture, people won't recognise you anymore. Like if McDonalds stopped using the M and instead had a clown face as their logo instead, the change would be confusing.