Hermione was a special case in many ways, they were already thought by many to be 'true loves' and she did save him from a Dementor, so it would be unlikely to count as a guarantee. Also Hermione did still have significant costs from this, she was imprisoned, exposed to Dementors, her reputation ruined and now she is bound to the service of the (possibly Dark) Lord Potter. So not an insurance scheme I'd be particularly willing to take up.