I had a 1.3 group to start, but one female was sold to me as a young rat when she wasn't and didn't ever produce so she went to be hawk food.
My male was the first to go after about 2 yrs, I left one young male in from a previous litter and the line continued. I have one unrelated group and the rest are semi related. I have 4 aquariums with 1.3 or 1.2 groups and one grow tank.
I feed hamster mix with dog food and keep wheels in all my tanks.

We named them from a Monty Python skit, Pudding, Sorbet, Cake and Tart...
Pudding was the last to go, she helped raise litters and was just a nice ASF... if there could actually be one.
She was a bit over 3 yrs old.

It may seem strange to be attached and to leave her alive all this time, but she did produce now and again but her last two babies, just didn't thrive and passed away before 4 wks of age.

Pudding.. will be missed.