I use standard csv import.
You can save date format with the profile but it is not saved without the profile.
When I import many different files I don't always use profiles (because it is faster and I can't delete the old profiles).
I'd like to see last used format in the import dialog. If it is not possible, maybe it is a good idea to include date format from Application settings in the date formats list of the import dialog?
Another solution is to add some other different formats to the list. For me the standard is yyyy-mm-dd.