I have used inline amps several times on excessively long cable runs. The amplifier enabled the receivers to reliably lock a signal that had been lost in the 500' - 1000' runs. Don't recall replacing failed units, but some models do have significantly better signal amplification with less noise.
In order to be a happy camper, understand the technology. The inline amplifier only amplifies the LNB signal level. It does not amplify the voltage or outbound control signals. Most modern LNBs have very high signal amplification and will not require or benefit from additional amplification.
The amplifier will likely have best performance if installed at the LNB, where the signal to noise ratio is at the highest ratio. There may be switching, polarity and motor control issues over longer coax runs. The in-line amp will not improve 22KHz/DiSEqC control signals and will not increase the voltages lost in the longer runs. You may find the signal traveling only 450' through RG11 has better Signal Quality readings (signal to noise ratio) than after inserting the amplifier.