That's what I mean, some devs start a new Play store app page for essentially what is just the next iteration/generation of the same app but now it costs again for those that previously paid for it.
But back to my original questions, what are people's experiences with app purchases and their update longevity?
That still depends on developers, not too many I have seen do that, and that's when they make massive substantial changes which does qualify it as a whole new app, going to the point of a complete rewrite and beyond, but then they still maintain the previous one with bug fixes.
As for the 2 you mentioned, I bought them like 10 phones ago with my nexus s.
On the flip side, you get developers that actually convert a paid app to a free one without including adverts, bugs or any other annoyances and continue to maintain it. SwiftKey and Fuelio are 2 such that I know of, I'd used swift for 2 maybe 3 years before they went free, Fuelio 18 months or less,that Dev was actually hired by a company to develop and part of his contract was to maintain his app, but make it free. So he still getting paid for it, just not by the general public.
I actually cannot think of an app that I had to rebuy, have obviously paid for better alternatives, either because the developer actually just abandoned it or another developer made something better enough. My previous fuel tracker was such a situation, I eventually realised the app I was using had not been updated in over a year.
You may actually find that a more likely scenario with Apple, with all the costs a developer incurs and the requirements apple has regarding support, and not to mention the company getting bored and writing new languages, while still expecting you to support order devices which use an older language.
Android your Dev cost is $25 every 37 years, Apple is $99 every year. Google has no requirement on OS support while apple requires you maintain a 3 generation OS support. That is one of the reason you often find seperate mobile and tablet versions on apple, while less often for Android.
Then again with Apple, devs make more money on free apps with advertising than on Android as on Android we can block such things.