Hello Oltion
It is not possible to change how many soft bounces must be received in order for us to stop sending emails to an address.
When an email address returns a hard bounce, it will be added to our block list and will be excluded from any further sends in which it is included. Addresses that return 4+ soft bounces in a 3 month period will also be added to the block list. You can find more information about excluded emails here: http://help.clickdimensions.com/excluded-emails/