I have heard that dreamsigns usually disappear after a few weeks and then get replaced by other signs, is this true?
For example, I recently started working as an ice cream vendor so I have naturally had several dreams about ice cream vans and such, but how long should I expect to have that dreamsign?
I guess there are DS’s that are constant, something from your everyday life, like a friend or a family member of something third and also there are DS’s that aren’t constant, DS’s that are caused by some changes in our life, like a new job and those don’t stick for ever, I guess when you become familiar with the job and people you meet every day on a new job that those DS’s will easily perish…
That’s my opinion, who knows maybe those things work differently… 
I noticed thanks to my DJ that a common Dream Sign for me was sitting in vehicles. But as soon as I started to concentrate on it, e.g. reality checking when using one in RL, those dreams stopped…so I think that could be true in some cases 
My dream signs basically change in every dream. The only constant thing is that they will be extremely out of the ordinary things that make me just know that I’m dreaming. Never had the same one twice. I don’t really have consistent dream signs like being at school or with family.