To learn when and how passwords are saved to stored session and remembered in memory please read:
https://winscp.net/eng/docs/security_credentials

Seo wrote:

...and every tot seconds or action user have to supply the new password again.

You probably refer to background transfers. Make sure you have checked Remember password of main session for background transfers.

2) propose a message to the user he/she wants to update the saved session with the new profile and so winscp automatically update the profile without any other step.

This is supported since 4.1 beta.

Suppose you are going to connect on a saved session for which the password has been changed. WinScp correctly require the new password to try again the login, but along the session the new password isn't remembered and every tot seconds or action user have to supply the new password again.

I think two things should be included in the next release:

1) on the scenario above, for the current session the new password supplied should be remembered until connection is closed
2) propose a message to the user he/she wants to update the saved session with the new profile and so winscp automatically update the profile without any other step.

Andrea