Tsubomi is not a veteran. She's an anomaly.
Being an A-lister for 14 years probably puts you in a 0.1 percentile as far as JAV goes.
I'm sorry, but you're comparing apples and lampposts here.
Yuma Asami's career lasted "just" 8 years. She wasn't a veteran either?
Check US porn, many actresses are in the business for 10+ years. Like JAV, a lot of girls just do few titles or stop once their first contract is over because they just wanted quick money for stupid things.
8 is closer to 10 than 6. Being in the business for almost a decade is a lot. Tomoda Maki started in 2003 and even if she had some break times, she's still active now. That's what I call a veteran.
Suzumiya Kotone, Mizumi Saki, Sunohara Miki, many girls started before Rion and are still active. Even Okuda Saki or Meguri, in the big boobs category started before her.
Like I said, when you compare with real porn actresses, 6 years is good but not to the point of being called a veteran.