The great thing about spider plants is that they reproduce by growing plantlets on the end of a long stem so if you get one plant then you can (unless it dies of course) have generations of new plants every year to spread around the house. My Nan had spider plants for over 30 years all from one original plant. As for me well i can claim a mere 10 years or so with various generations of spider plants from a couple of plantlets i took from the plant in my boss' (at the time) office.
Once i had over a dozen plants but that dropped to 2 over time, but now i have taken 4 of the plantlets for a new generation. I don't think the 2 "parents" are my original spider plants, to be honest i should have kept track which were the originals! But never mind the spider plants live on for a new generation!