This picture illustrates perhaps the number one problem with low voltage light fixtures using Bi-Pin MR16 type lamps. Shown here are the two contacts that were inside the socket of a fixture using an MR16 lamp. The top contact is very corroded due to a loose connection with the pin of the lamp. These loose connections, which seem to be common in all low voltage MR16 type fixtures, become very hot and cause this corrosion.
The rate of corroding of the contact depends greatly on the amount of time the fixture is used. If you will be using the lights for many hours per day, and you don't enjoy repairing things, then opting for MR16 type fixtures might not be a good idea. These fixtures work well, and last a long time, when they are used sparingly.
LOW VOLTAGE FIXTURES USING MR16 TYPE LAMPS