Let me start out by saying that slate tile roofing is expensive, but if you have the money and you are building your forever home then it can certainly be worth it.
Hard slate roofs can last from 75 to 100 years. That means if you are going to stay in your house for a long period or plan on passing it down to your children, then it can be worth the investment. There is also "soft slate" that will last from 50 to 125 years.
If you factor in 5 roof replacements over the lifetime of your home, then the slate can pay for itself (but if you plan on moving around then we would not recommend it).
Slate has the added benefit of being fireproof, and highly wind resistant.
If you want the look of slate, but not the high price tag or challenging installation, there are also companies that make imitation slate. These options are durable, look great, and are less expensive than slates.