Back Set Question

[Boda Getta]

I was cleaning up my still area and discovered a 6 gal water jug of back set I had forgotten. It is about 4 years old and was sealed air tight. There is no mold but the back set has separated into 2-3 levels. I have used back set before with good results and prefer sour mashes but have never used one that old. I usually ferment in 32 gal batches and are thinking of dumping this back set into my next batch, any of you guys think of a down-side or a reason not too?

BG