First, some information to help you make a good choice. The products follow. A much smoother taste can be obtained with pump type espresso makers. To maintain the macchinetta in good condition , wash all the parts thoroughly with hot sudsy water, and rinse thoroughly. Keep the heat source as far away from the handle as possible, to prevent it from heating or burning.
Gaskets are likely to last at least a year if they are cleaned on a regular basis.
The Overpressure Plug will last many, many, many years. The plug is a safety mechanism that will open a way for the steam to escape if it can't go though overly tamped coffee grounds. Occasionally scour the inside of the macchinetta to remove mineral deposits. Some discoloration may develop on the inside and a little on the inside. This is perfectly normal, due to the repetitive heating and the effects from your water supply.