I am designing a high precision DC measurement system that needs to maintain its accuracy over time and temperature. Which amplifier is best suited for this?

For the highest level of amplifier stability over time and temperature, zero-drift amplifiers are a great choice.  These amplifiers operate in a way which essentially eliminates DC offset errors and low-frequency 1/f noise.  ADI offers several op-amps current-sense amplifiers and instrumentation amplifiers which employ this technique.  More information on zero-drift amplifiers and their benefits can be found here: Zero-Drift Amplifiers in High Precision Circuits | Analog Devices.