Personality view disappears at once at the stage of stream entry or is it gradual ?
I guess you mean identity view (sakkāya-diṭṭhi) - please see this question for examples.
Eradicating identity view is different from eradicating all traces of self - please see this question.
A view is a kind of belief. For example, a person may have the view that the Earth is flat. However, this person may change his view, based on the opinion of trusted credible scientists, without making a direct scientific validation of his view.
Views may affect one's behavior and in turn result in particular outcomes. For example, if you have the view that you don't have to clean yourself when you get dirty and before you eat, this may cause you to contract diseases due to lack of hygiene. By changing your view from the wrong view to the right view, you can reduce your suffering.
But you don't have to change your views on hygiene after experiencing disease. You can adopt the right view on hygiene, after listening to trusted credible sources.
Similarly, the Buddha is the trusted credible source who taught us that all phenomena is not self. He also taught us that eradicating self view will reduce suffering. For example, when someone insults you as being fat, you may become angry and experience agony due to the fetter of conceit, but you can snap out of it quickly and not dwell on it, due to your not having the view that your body is your self. By snapping out of anger quickly, your suffering will be reduced. And that's how not having identity view will result in the reduction of suffering.
You don't lose your identity view after stream entry. Rather, you have to overcome identity view in order to reach stream entry. You don't lose the wrong hygiene view after becoming hygienic. You have to lose the wrong hygiene view and gain the right hygiene view, in order to achieve a good state of hygiene.
A stream winner could become angry due to clinging and conceit (tanha-mana), when someone insults him as being fat or stupid. But he would snap out of it quickly, due to not having identity view. Conceit is a deep-seated tendency that is hard to uproot. But a view can be changed through learning, reflection and understanding. A fully enlightened arahant has uprooted all the deep-seated fetters. Please also see this answer.
Eradication of self leads to perfection which is nothing but Nirvana. Continuos meditation on five grasping aggregates leads to the fruit of stream enterer, once returner, non returner and perfection.Continous meditation on five grasping aggregates leads to utter realisation of Anatta. I quote the following from sutta SN 22.122 which says that even the perfect ones meditate over the five aggregates:
But Reverend Sāriputta, what things should a perfected one properly attend to?” “Reverend Koṭṭhita, a perfected one should properly attend to the five grasping aggregates as impermanent, as suffering, as diseased, as an abscess, as a dart, as misery, as an affliction, as alien, as falling apart, as empty, as not-self. A perfected one has nothing more to do, and nothing that needs improvement. Still, these things, when developed and cultivated, lead to blissful meditation in the present life, and also to mindfulness and situational awareness.”
This question investigates whether Nirvana means utter realisation of Anatta. My opinion remains that Nirvana means Anatta. However from what I have quoted above ,the answer must be clear to you that meditation over the aggregates (which denies existence of any self) is continuos meditation. It should never end.