The Honeymoon for Presidents in this country usually only applies, in a real and practical sense, to their first term in office. We can use President Obama as an example, but really it is true for almost any first term President. When they are elected and take office, they haven't done anything yet. What people remember are the promises of the campaign, and their hope that things can change and improve in their lives and the country under the new administration. While there are no accomplishments yet, there are also no failures, disappointments or liabilities.
For some Presidents, the honeymoon is shorter than others. George W. Bush had a fairly short honeymoon because his election in 2000 was controversial. John F. Kennedy had the failed Bay of Pigs invasion only three months into his Presidency, and it overshadowed and stymied his efforts to do much else in that first year. Ronald Reagan, on the other hand, was able to extend his honeymoon for several months because 1) the Iran Hostage Crisis ended as soon as he took office, and 2) he was a fantastically motivating speaker.