Budgies can live up to twelve years, in some cases.
Sadly, just as with every creature, there's no definitive age that any one species will live to reach.
As your first budgie was very small and died so young, it was possibly because of an unethical breeder.
Although your current budgie is sick, taking it to an avian vet tomorrow will give Santi the best chance. Budgies do take a while to show any illness, but that doesn't mean that all illness is fatal.
For now, you should cover up Santi's cage on three sides to reduce any stress and feed millet soaked in pedialyte solution. There's a recipe here: Guardian Angel // Pedialyte // Pedialyte Recipe
Even with being from a breeder, sadly it is not an indicator of good health.
An ethical breeder can only do so much.
What type of diet is Santi on?
Please keep us updated on how the visit to the vet goes.