I have to agree with Teromous. Your getting better as a brewer if your numbers rise slowly and not swing.
There are way too many variables to control as a homebrewer to get consistent EFF%. Unless you are in an enclosed evirmonmentally controlled, automated, exact crush, exact water, exact everything you wont ever hit 99%EFF. But small things that you do as a brewer helps you learn and get consistent EFF% and over time your learned behaviors will begin to produce 70%, 85%, 90% EFF.
60% EFF drinks as good as a 90%EFF....I dont ever recall someone saying, "Man, this beer sux! You can really taste the %EFF in their mash and it was pitiful!"