I have a widget that helps looking for posts in my site.
Here's a picture of the widget (site's not online yet)

I want to use html5 session storage to store the widget options among pages.
When a new page is load, the widget switches to the saved state and shows the results made with the saved options.
I'm in doubt among 2 solutions about when storing the widget data:
To store the widget state when the user trigger a search (the blue button) so that the new page shows the results of the previous page, with the drawback that if the user doesn't trigger the search before changing page, those option changes are not saved so the user will find options different from the one he left in the previous page.
To save the state when the user changes the option and load the new page with the results. the drawback is that again if the user doesn't trigger the search before leaving the page, this time he will find results that differs from the ones he had in the previous page, because they are calculated using the stored options.
So, is it better consistency in the results or in the options?
One solution could be to trigger the search on every option change, but i'm afraid to overload the server too much with the ajax requests.