We would expect 3-5years but many customers have had them working for far longer.
The only issue I can think of is the angle of the gutter/light. I'd suggest testing one with a clip first.
Sorry we don't sell spares currently for the Curve Solar Motion Light.
The sensor will detect motion up to 3m away.
We don't at present. We've had customers successfully fit this light to gutters though with small screws and silicone to seal the holes.
The Curve works well all year round, provided you don't install the light on a north facing wall.
It is estimated at 80 lumens.