You also might be referring to an elastomeric?

Most paint companies have similar products to these.

It sounds to me like you are trying to get away with one coat - no primer - and want it to last???

Do yourself a favor - regardless of the claims the manufacturer makes follow good painting procedures:

1. Clean - remove dirt/chalk/mildew
2. Scrape - whatever will come off.
3. Prime - with a top quality primer - I prefer oil on exterior wood - but latex is ok too.
4. Patch/caulk - any holes or cracks - with a top quality exterior caulk or patch.
5. Paint - with TWO coats of 100% acrylic exterior paint - top quality.

Use a great product - follow these steps - and it will last a long time - don't, and it won't!

Mr. Paint

There is no paint that will last a life time and if it does not all they will give you is another gallon of paint if you still have the receit that is.