hello to all! ive just whipped up some gritty mix for my plants but i could only buy large quantities of the ingredients in my area and i was wondering about the left over mix if theres any reason why they wouldnt keep in a large plastic tubaware container with a lid on it until im ready to use them next year or whenever that may be? or will it break down on its own?

also the only granite i could find was 1/4 not 1/8`` so how will this effect my mix and will everything be okey if i just watter alittle more often?

thanks in advance
chris