There are many types of thatch available. Depending on which part of the world and your specific needs, there are thatch panels (or tiles) to be found that can be very accommodating. Some people find the Brazilian tiki thatch to be completely waterproof, lasting up to 15 years.
Reed thatch, often used in Japan as insulation, is said to have exceptional thermal efficiency and is rot, mildew, and wind resistant. The life expectancy of reed thatch averages 10 years. The photograph below is an example of a reed thatch panel sold at Forever Bamboo
Many people designing with an island theme in mind often use the popular Palm leaf thatch, also known as rain cape. If maintained in a warm, dry climate, the palm thatch or rain cape can last up to 6 years.