Gambling with the Hubble?

A recent news item about the upcoming fourth Hubble servicing mission
notes that it will involve an unprecedented step where instead of
simply swapping out two Hubble instruments, those instruments will be
repaired in space through replacing individual circuit boards.

In itself, that is good news. But further details in the report make
me wonder if they're not going a bit too far. (Of course, there may be
valid reasons for what they're doing as well, such as the difficulty
of achieving appropriate clean-room conditions aboard the Shuttle.)
Opening the instruments, and replacing the individual boards, will be
done during the EVA, rather than taking the instruments out of the
Hubble on one EVA, repairing them on board the Shuttle, and then
replacing them on a second EVA.

John Savard