It's a valid concern. AWS has been around for many years now with numerous services. Has there been a single offering which they retired or stopped supporting? I'm not aware of one.

Amazon doesn't just create services, throws them over the wall and see if they stick. Rather, they almost always RESPOND to customer requests. Dr. Werner Vogels, AWS's CTO makes a point about that approach at about any keynote he gives. Similarly, they try to also avoid feature creep by only providing features which customers really ask for.