For me it's time...I'm lucky if I get to brew once a month due to a crazy schedule and that of 2 young kids, so yes, I have this dilemma every time I ponder what my next grain bill will be. Sometimes though, it gets overwhelming just trying to figure out what to brew next, so today I just brewed a SMaSH for the first time. It was kind of relaxing to only have to measure out one grain, and one hop strain...
Packaged: Heady Topper Clone, Graff, Basic Spiced Cider
Recent Meads: Mead Day '11 Ginger Metheglin, Mead Day '12 Traditional (orange blossom) Mead, Fresh Simple Cyser '12
Primary: Wild Cider, Simple Cyser
Secondary: Why do I keep this line here...?
Bulk Aging: Cocobochet
Planned: Hop Metheglin #3 (NZ hops), Trad. Gesho T'ej