The "temporary protection" at Bassae has been there a lot longer than "a couple of years" - since 1987 in fact. The 2004 ICOMOS "State of Conservation Review" did not expect its removal in the foreseeable future :-
".. installing a temporary protection cover on the monument (1987)...... Over the past 17 years it has been proved that the shelter protects the temple's fragile material from the direct effects of weather phenomena and it has contributed decisively in halting the deterioration of the stones. Despite the fact that the form of the shelter expresses its temporary nature, and it differs from the architectural shape of the monument, the scientific committee is exhaustively investigating the matter in order to find a permanent solution for the protection of the temple"
This linkhttp://www.fordham.edu/gsas/phil/babich/Babich-From%20Van%20Goghs%20Museum%20to%20the %20Temple%20at%20Bassae.pdf
has a rather intellectual, but possibly interesting, philosophical discussion from 2003 on the concept of "preservation" by separating historical objects from their context by "taking Heidegger's discussion of the strife between earth and world to the site of the ancient temple of Apollo Epicurius at Bassae as an example of the insistent foreclosure of the ancient work of art and the conflicts of the pervasive efforts of modern conservation". If that proves too cerebral it also contains photos of said "temporary protection" which it describes as "a weirdly circus-like structure of ungainly proportions, the covering tent builds the closed space of modern vanity – a permanent temporary scaffolding – around the temple: a mindless gesture of affected protection from the elements, secluding and so refusing them as the elements which the temple was first set up to articulate" !!!!