Is 1.5mm too thin for daily wear?

It is on the delicate side. At 1.5mm the band is fine for everyday wear if you are not hard on your hands, but it will flex more than a 2mm or wider band and thin further over decades of wear.

What does grain set mean?

Small metal beads are raised between the sapphires and pushed over their edges to hold them. That is what creates the beaded line you see along the band instead of a smooth channel.

Why a half eternity instead of a full one?

Stones run only across the top half, so the back of the ring is plain gold. That makes it easier to resize and cheaper to make than a full circle of sapphires.

A half-eternity band with a plain shank can usually be sized, unlike a full eternity. Because it is custom-made, ask the maker before ordering, since sizing work on grain-set stones needs care.

How should I care for the sapphires and white gold?

Clean with warm water, mild soap and a soft brush, and dry fully. Avoid ultrasonic cleaners on grain-set stones. White gold is rhodium-plated, so expect re-plating every year or two to keep the white color.

Does it work as a wedding band with an engagement ring?

Yes. The 1.5mm width and low grain setting let it sit close to most slim solitaires, and the blue stones contrast with a diamond without competing with it.