I dont think advisor would dump the coin after ICO since they are a part of the team. They probably wouldnt join in if they didnt believe in the success of the project.
I am sure its mostly bounty hunters that are responsible for after ICO dumps.
Truth to be told, advisors don't owe anyone anything, and they can dump it all when ever they want, they are just offered basically free money for some thoughts and publicity.
I think it's up to in which project they are involved. If they see a great future for one project they will probably hold the tokens. If they think there will be no growth for a longer time, I could imagen that even advisors dump coins to get nice money out of it.
They should have decide it before they join the team, because why would they join the team if they didnt want to support the project? Too much effort if they just want to dump the coin/token.
Sure they are smart people, and that's the point. Of course they want to make money, you don't believe they would work for free, right?
Also there is a possibility that a project looks good and interesting before, but it develops in a totally different way. I am pretty sure that they, if they see the need, also would sell instead of holding. But who I am, I am not an advisor
Advisers are also good to prevent mistakes. They have experience often in buseniss and crypto. Makes can be avoided with an experienced person looking over your shoulder.