Question

what might be a long term benefit for the nation from space exploration

Answer 1

international kudos/reputation.
international friendships through mutual collaboration and respec
commercial value of the expertise gained through the technology needed for one of the harshest and most demanding scientific environments known to man.
http://perendis.webs.com

Answer 2

find somewhere else to live :-)

we are after all trashing this lovely little planet at a rate of knots.