It makes me nervous as well ... but I'm patient, and am happy to wait until sims die if necessary ... Gen 3 is a male, and so can produce Gen 4 as an elder if necessary.
EDIT:
I'm sorry, I thought it had been longer in game than 4 days (Yes, I'm at day 1 week 14, and Javert is now a young adult, and aged up with the Family Orientated Trait (Traits are Photographer's Eye, Family-Orientated, Artistic, Adventurous and Genius). He is level 7 as SE Photographer, and has 10 celestial discoveries, 30 hours of tutoring sims, and 2 chess ranks to go before supermaxing logic. Six of his current house mates can all be tutored in photography (its a free family skill, as is painting, athletics and martial arts), and I expect that'll get him his hours up for tutoring sims.
I've redesigned the house, moving various skilling rooms downstairs off the bedrooms of current and future targeted to be immortals (and only accessible through the relevant bedroom). The doors to the bedrooms are keyed to allow only the targeted immortal, and all mortal members of the household through them. It took me a while to workout that's why Javert couldn't use the bathroom off Gavroche's bedroom for his YA hairstyle and clothes re-do.
Rusty Galah has mixed 71 vials of bliss, and countless other types of elixirs of various kinds and is now writing. His latest book was the Fantasy Book "The Money Making Book - The Beginning of the End Part 1".
Current museum value without any of Javert's YA pieces is 121,423.
Cosette was heard saying "The Immortals that Paint Together Get To Eat Ambrosia Together" the other day, yes, I intend to supermax painting for each immortal.