At the last minute, the Obama administration gave consumers more time to sign up for health insurance starting Jan. 1. People will now have until the end of Christmas Eve, giving them an additional day. The administration hopes a late surge of enrollments will boost numbers, which have lagged far behind expectations. The insurance industry is hoping the same thing. But it is also expressing dismay over recent changes to the law that allow some people to opt out of the individual mandate or purchase plans otherwise prohibited under the law.