the dusty environment argument is old, your car has a airlifter, its there for a purpose not for show:P it'll take care of the dust, using oem air filter would be better and it can be used till 10,000km or 8000km if you are following long drain interval.
according to these dusty environment suggesting gurus i wonder what they say about cars in middle east, dubai, africa etc where theres a lot more dust and lot more heat, even in some states in america they have lots of heat and dust they must change their oil at every fuel fillup??? no instead they use even longer intervals because dust doesnt say much, you can follow the severe conditions in owners manual which includes dust but mostly stop start low speed driving and use that drain interval, a fully synthetic has more purposes than just long drain intervals, engine cleaniliness is one of them.