The bass I've had the longest is my 2004 Epiphone Les Paul Standard, which I acquired in early 2009 and stock it looked like this:
It was subsequently tricked out with EMG-HB pickups, an EMG-BQC 3 band EQ, John East knobs and a pickup selector switch in the usual LP location:
I then stupidly sold it. Then I found it and bought it back. It acquired Schaller straplocks on its travels. Then I got bored of the EMG sound and also wanted to make it black and gold. So it got gutted, then rebuilt with DiMarzio X2N-B pickups, a Babicz bridge (only there because I couldn't find a gold three pointer for love nor money), gold Wilkinson tuners and a passive VVTT setup with series/parallel push/push pots on the tone pots.
So yeah, I've had this bass on and off for about 15 years. I did some of my earliest gigs with it, and I guess it's going to stay with me. Not my first bass, but probably my first "good" one.