The HST is best at refining existing information (so, perhaps adding more), providing us with better pictures or better measurements. For instance, before the HST, the age of the universe was known as to be between 10 and 15 billion years...the HST put it at 13.7 billion years with a margin in the million years rather than the billion.

But the very way it is giving time to teams of astronomers makes it impossible for major discoveries.

Teams must present a project which will be examined and accepted if chances are high to produce expected results. There is no room for wild speculations, theories against what is generally accepted. There is also no room for frequent repetitive use of the HST (many other teams are waiting for their turn). In a way, conservative peer revewing and lack of time go against major discoveries.