I think it has more to do with Hobbits innate will and magic resistance. Smeagol for instance killed his best friend over the ring having only held it for minutes at most. The ring did have it's hooks in Bilbo but his Hobbity-ness combined with a good friend(Gandalf) asking for him to give it up let Bilbo control himself enough to drop the ring. These are just my thoughts and interpretations though.
Besides this, Bilbo used the Ring sparingly, so the Ring didn't have as much influence over Bilbo (despite him owning it for a long time), and this allowed Bilbo to give up the Ring more easily. That said, Bilbo was none too enthusiastic to give up the Ring - Gandalf had to mildly threaten him before Bilbo was convinced to give it up.
Yes true, the signs show that he gave it up willingly, but I was just thinking if this might be and if there may be anything about it, as I could not find it :)