I've had one for about 4 years. Three in the ground. This year there has been very little damage despite the hot weather but last year most of the leaves were burnt off. I agree that they become a bit more resistant as they mature.
Leaves grow faster than roots. When the root system catches up it will be better able to support the top but you still need to keep it watered when it's hot. They don't care for wind either. They are lovely when they get going though.
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Watch it doesn't dry out too much. If it's in a very sunny site, the foliage ends get fried very easily.
I live in west central Scotland - not where that photo is...