: fq=gender:f&fq=( friends:y )&fq= country:us&fq= age:(18 || 19 || 20 || : 21)&fq=photos:y
that would be my suggestion based on waht i'm guessing your typical use cases are ... but it's really hard to infer patterns from only a single example URL. the queryResultCache isn't nearly as interesting in cases like this as the filterCache is ... your filterCache doesn't even need to be very big to give you huge wins for the type of use cases i'm guessing you have. -Hoss
