I'm wondering whether it'll work out cheaper to treat my 4 hens with Marriage's pellets with Flubenvet (I'd only use 3.5kg of the 10kg bag before it went out of date) or to use the 1% dilution & add it to their regular Smallholder pellets. I gather that 60g of 1% Flubenvet costs around £15 depending where you get it from, whereas I've seen the treated pellets online for around £7 / 10kg. What's the shelf life of the 1% powder & does it need to be kept in the fridge?