I work in reward for a general insurer in Australia with about 300 people in broker-facing sales. We ran 14 SPIFs last financial year, mostly gift cards or a few hundred dollars for selling a particular product in a particular month.
I finally compared sales of the targeted product in SPIF months against the months either side. For 11 of the 14 there was no measurable lift. For two there was a lift followed by an equal dip, so we paid to move sales forward by three weeks. One worked, for a genuinely new product.
My view now is that SPIFs are a habit sales leaders have, more than a tool. We have cut to a maximum of three a year, each needing a stated baseline before it starts. Has anyone else measured theirs?