J2 offer a similar pattern with their Optional Winter Leave. They usually have 5 variations or you can put your own idea forward for consideration. Up to 5 months is usually available.
I'm tempted with the BOGOF offer e.g. taking 5 months off and only losing 2.5 months salary. You're not on standby, but I gather there is a contract term that allows the company to bring you back if necessary.
People go travelling, education, or just get away from work. I'm considering it to give more time to my self-employment, which requires much more time over the Winter months (retail).