From what you said above it sounds like Microsoft should also still be releasing and providing you patches for Windows 95. You paid a one time fee for an application, if you wanted support and updates for it forever you should have expected to be paying a monthly / yearly fee. If at the time the updates stop coming, then the company should just stop charging you the ongoing support fee.
Expecting lifetime support for a one time flat payment of almost nothing is pretty silly.
The "lifetime support" argument doesn't follow from anything I said. Users may not have been savvy to the possibility of the software being discontinued in this fashion, but they certainly understand that an end-of-life is inevitable. They're used to free updates over the natural lifespan of the product, and they feel that there's been a breach of courtesy when the natural lifespan of a product is willfully cut short.
I don't know. I know that Windows 95 has long since reached the end of its natural lifespan, and that users feel that Sparrow's life was "cut short". I'm sure there isn't a sharp dividing line, but we don't really need one in this case - it's clear which side this falls on.
Expecting lifetime support for a one time flat payment of almost nothing is pretty silly.