Renting does not have to involve a lease, as in being time-limited. Renting can be open-ended.
The key differentiating characteristic of renting vs buying is that in renting ownership of the expected good has not changed or has not fully transferred.
When you buy a good, legal ownership (whatever that means in any given jurisdiction) of that specific good has been transferred in full.
Entities using DRM are exploiting not the ownership transfer but the expectations for that good. The corporate, as it almost always is, transfers ownership of a substitute good which requires a license/renting to access the expected good.
The end users therefore have not bought the expected good, but a substitute good plus an access license "option". With DRM, this "option" can be (technically or legally) revoked or is callable at any time thereby disabling access or removing the expected good.
So, the obvious solution is not to buy a substitute good + callable option when you actually want the underlying (expected) good. Otherwise, you are just creating demand for substitute goods and all the fancy methods to create the callable options.
Ownership does not have to be "transferred in full" for something to be a purchase. They key difference with rentals is the lack of time limit or reserved right to revoke the license. The fact that the purchased rights may be fragile does not make it a rental.
I can sell you an easement on my land. It's a purchase, not a rental. But it can be a very limited right nonetheless (e.g. Just the right to cut across the grass to the road). I can sell you a car on the condition you don't repaint it. I can sell you a piece of land on condition that you only use it for a certain purpose. These are all purchases within the common use of the term, even though they effect a partial transfer of rights.
The discussion above is not about formal definition, but about common perception. Common perception of buying is getting full ownership. All other cases are far less common.
In general, the whole notion of attempting renting the content obscuring it as a sale is not a honest way of doing things. And using DRM to enforce those rental limitations makes it even worse, since it uses unethical preemptive policing methods to do it.
The key differentiating characteristic of renting vs buying is that in renting ownership of the expected good has not changed or has not fully transferred.
When you buy a good, legal ownership (whatever that means in any given jurisdiction) of that specific good has been transferred in full.
Entities using DRM are exploiting not the ownership transfer but the expectations for that good. The corporate, as it almost always is, transfers ownership of a substitute good which requires a license/renting to access the expected good.
The end users therefore have not bought the expected good, but a substitute good plus an access license "option". With DRM, this "option" can be (technically or legally) revoked or is callable at any time thereby disabling access or removing the expected good.
So, the obvious solution is not to buy a substitute good + callable option when you actually want the underlying (expected) good. Otherwise, you are just creating demand for substitute goods and all the fancy methods to create the callable options.