Longest time spent tweaking ONE track?

I'm curious: What's the longest period of calendar time you've spent in tweaking/perfecting a single TRACK (not an album, but a single track)?

What aspects of that single's production were you most desirous to "get right" ?

What, to your knowledge, are some of the legendary time periods in the music industry regarding this?

Thanks in advance,

ras

so {censored}ing long i almost killed the drummer. i wanted the band to fire him immediately... but they wouldnt do it [pussies]. i actually created a different beat for the choruses using part of his original beat but making it actually FIT the song.