Some interesting details.
Wand's first UFC/Pride fight was Oct 16, 1998: the famous TKO loss to Vitor. So that's 20 years. He fought a few times in IVC in 97, too, which is nothing to thumb your nose at.
Rampage fought in smaller but well known promotions before his Pride debut, where he was choked out by Sakuraba on Jul 29, 2001. So that's 17 years for him.
Shogun didn't debut in Pride until 2003. So if you count 2018, that's 15 years of service.
Hendo debuted in the UFC in 1998 (the tourney win over Carlos Newton)... but he wrapped it up in 2016. So that's 18 years.
Big Nog was Pride, Nov 2001, but wrapped it up in 2015.
Barnett was UFC against Gan McGee in Nov 2000, but he hasn't fought since 2016... 16 years.
Kharitonov, Pride 2003, but he's primarily fought in smaller promotions since 2011 (sad face)... so that's only 8 years.
OVEREEM: actually deserves some credit here. His Pride debut was 2002, so 16 years... but he fought in RINGS since '99... like IVC, nothing to thumb your nose at.
HUNTO: I think he comes out the biggest winner in this conversation, even though he was froze out by the UFC for a few years mid-career. His Pride debut wasn't until 2004 against Yoshida, but he fought 20-something times in K1, including the GP title victory, between 2000 and 2003. Let me say that again. 20 high level kickboxing fights in 2-3 years. That's fucked. That's way more of an accomplishment than fighting 2-3 times a year in the UFC. I guess there were a lot of one night tourneys in there... hmmm. I'm counting it 18 years for Hunto, and few have fought tougher competition over that time period.
And of course, the grand daddy of them all, Vitor. Debuted in 97 against Tre Telligman, with the tourney championship in there. He fights Machida soon, so that's 21 years.
Machida: KO'ed Rich Franklin in Inoki's NYE promotion in 2003... 15 years.
I'm being a real asshole about Tito... he's a pioneer, carried the sport for a long time and debuted in 1997. But as far as I'm concerned, he hasn't taken his career seriously since 2006 against Forrest Griffin. I'm going to leave it there.
Shammy, same thing: he fought in the original UFC back in 93 and he's kept busy up until 2016. That'd be 23 years, but unlike Tito, I can't even look back on his career and figure out where it started to be bullshit. I don't know. I feel like a piece of shit about this one. He has some very obvious big wins over guys like Funaki, Bas, Matt Hume and Maurice Smith. But there's also some long breaks in there, and he started working fights almost as soon as he began fighting.
I think the big winners in this conversation are Hendo, Hunto and Overeem. I knew Wand would do well, but I didn't realize it was the full 20 years for him.
Very refined company.