Hi Keith,
Silicone furniture spray will (most probably) be a water based mix of silicone oils and waxes, and petroleum or natural waxes - the silicone waxes will be OK on rubber, but I'd suggest you don't let a petroleum wax anywhere near rubber.
Silicone spray (from Halfords or similar) is a mix of silicone oil in a solvent carrier - this will work really well on window rubbers. Spray onto a rag and wipe around the rubber.
Silicone oil (Thetford toilet seal lubricant) is a bottle of pure silicone oil - pretty much identical to the maintenance spray, but without a solvent carrier. Need to apply with a cotton rag - but it lasts for ever.
WD40 and Vaseline - are petroleum based and will make rubber swell up and go very sticky - avoid...
Robert