9-Eye may be the assistant to Timekeeper, but she was the one who did all the actual time-travelling.
Timekeeper stayed behind in 1995 to run things because… someone had to. Why not the guy running the experiment? There was no way he was envious of that.
Although 9-Eye was the one to meet Jules Verne and HG Wells and Leonardo da Vinci. Sure, met Jules Verne himself when he'd accidentally brought the writer back to 1995. That was good enough for him.
He wasn't envious. Not one bit. And if he was, 9-Eye would definitely chew him out for it.