Are Bill and Ted immortal?
The New Testament isn't the only fictional saga that parallels Bogus Journey. De Nomolos' scheme mirrors that of Skynet in Terminator, except he programs Evil Robot Bill and Evil Robot Ted to sabotage the genuine articles' careers and romances once they're out of the way.
Robo-Schwarzenegger would call De Nomolos' plan redundant. Why doesn't he expect his preferred version of the future to unfold the instant Bill and Ted cease to exist? Why do the Evil Robots need to take over Bill and Ted's lives, brutalize Princess Joanna and Princess Elizabeth, then deliberately botch the battle of the bands Wyld Stallyns are supposed to win? Why bother with Evil Robot duplicates at all? Why wouldn't Nomolos simply go back in time himself and decorate a wall with Bill and Ted's grey matter? Because Bill and Ted are immune to the natural order of space-time.
Tellingly, when the authentic Bill and Ted arrive at the San Dimas Battle of the Bands, the movie's grand finale, their cybernetic counterparts do not appear the slightest bit surprised to see their recent murder victims galavanting about without a scratch on 'em. Neither does De Nomolos, when he drops into the scene shortly thereafter. Everyone is in on a fact that is never conveyed to the audience. Bill and Ted are immortal.