S-l-o-w fermentation on EC1118

[fahdoul]

I've got 2 5 gallon washes going, basic sugar washed with a bit of tomato paste, molasses and yeast nutrient, using Premier Cuvee (blue packet) Red Star, which I am told is pretty much the same thing as EC1118. I use that yeast because I am trying to get a reasonably high alcohol percent and its what the local homebrew shop has.

Problem is, whenever I do this and aim for a medium high % of 16 or so, the fermentation slow down until with about 7% left to go progress is almost undectable. The wash is still bubbling, but just barely. If I stick it in a carboy at this point and leave it for several weeks or months it will eventually, from past experience, finish fermenting and clear, but it takes forever. Pitching another packet of yeast in will bring renewed vigor for a day or two but then it settles down to as it was.

I seem to recall this yeast strain is just slow, but this seems awfully slow. Any advice how to speed it up?

Oh, fermentation temp is about 70F.