Thusly Sean Spake Unto All:

How big are the neons? They only have a life span of about 1 year, and often
the large ones are 6-9 months old by the time they are sold in stores.

True about them being 6-9 months, not true about their life span.
Their maximum lifespan is about 10 years. I personally have tetras
which have been with me for over 2.5 years.