I use "MP3 Splitter & Joiner Pro 5.0" and can recommend it if you want to give it a try to split the long file down to shorter durations, run it through that site, then merge the individual isolated tracks back into a single file.
I use it to split a long audio file (many hour audio books) into multiple files (chapters). http://www.ezsoftmagic.com/mp3splitter_joiner_pro.htm
I haven't looked at what the 'free' version lacks in features/locks off. If you would like to try the non-legitimate pro version, I can provide you with it.
It has many options, including silence detection for automatically splitting the long file into segments based on duration of detected silence (such as between chapters in audio books).
There are also other software like it, but I haven't tried any of them.
ffmpeg will split an mp3 (or most anything else) losslessly BTW.