The longevity of iPads remain poor because iOS updates slow devices down and downgrading is still not a possibility. Sometimes updates to the latest iOS are even forced if you want to run the latest versions of some apps.
To keep it short, the iPad is device with planned obsolescence, and will depreciate and get slower over time.
Good observations. Even if one holds off in updating iOS to a new version, the requirement by some apps for the latest version will put pressure on people to update iOS in order to use those apps.
When most people think of "planned obsolescence" they're thinking of an explicit decision made in some back room in Cupertino to limit the lifespan of their iOS devices. That is not how it works. It is a multifaceted approach of small on-the-surface innocent or defendable actions that individually don't draw attention, but in combination accomplish the goal.
Here are a few of those actions that contribute to planned obsolescence...
- New hardware features introduced in gen x that are then perfected in gen x+1 (the inferior experience of gen x incentivizes a person to get gen x+1).
- Preventing the customer from downgrading to a previously supported version of iOS.
- New features introduced in iOS that require more resources than previous version.
- Requiring apps to incorporate OS-level features (eg. multi-window)
- Default settings in development tools set to require libraries of latest version iOS (that could otherwise work with older versions)
All of these topics have been discussed in various threads and there are "innocent" explanations for all of them that a reasonable person could agree with or accept. But they have a cumulative effect that results in obsolescence. No one is forced to buy a newer model device. The customer has to make the decision to do that.
I won't even get into the psychology of people saying that their "upgrading" their iOS devices to describe buying a newer model, as if they're popping in some more RAM or swapping in a faster processor.
If someone thinks that Apple has short-changed them on the life of the product they purchased, the LAST thing they should do is reward the company for that action by buying ANOTHER (and probably more expensive) device from that company. But that's me, and I'm an oddball.