Yes some anacondas do eat their mates after they mate.
Not all anacondas will eat their mates though but some do.
Usually after mating the larger female anaconda will eat the smaller male anaconda but they don't always do that.
Anacondas have a lifespan of between 10 to 12 years.
As long as the Anaconda doesn't get killed in the wild or get some disease or consumed by some other animal then the Anaconda can live as long as 12 years and if they are lucky they may live a bit longer past their lifespan.
When people keep Anacondas as pets then they usually live their lifespan but out in the wild they may die sooner due to predators.
A female Anaconda can give birth to as many as 20 to 40 baby anacondas at one time and the baby anacondas are 2 feet long and they are capable for individual life from the moment they are born.