They last as long as gold. Many dentists feel that indirect composites are a bit softer than gold and more like real tooth. They look like real tooth. Indirect composites are fairly new and many dentists don't know how to place them properly. Always find an experienced mercury-free dentist to place indirect composites.
Indirect composites are just as expensive as gold.
When an initial amalgam filling is placed in a tooth that has never had one before, a larger amount of the tooth has to be drilled away. If a small composite is placed for just a few more dollars, less of the tooth must be drilled away. This larger amount of drilling weakens the tooth hastening the day when tooth will need an expensive crown, root canal or when it must be pulled. Small composites are only a few dollars more expensive than amalgam and last just as long. At the very least, once a large amalgam filling has been placed, it must be replaced either with another amalgam or with a much more expensive indirect composite or gold inlay.