Posted: 30/06/2015 at 12:44
I would imagine that the decomposed material will be fantastic stuff.
If the grass has just turned to slime, then do not despair, dig a trench across an area where you want to cultivate and bury the 'slime' and cover over with soil. It will soon be incorporated into the soil by good old worms and bacteria.
Our 'non-compost' heap is used about every 5 years and the stuff in there is really good despite being made up of all sorts of roots and such like which cannot go on the heap proper.
Length of time means little.