In late 2008 I realized that I would be flying 24k miles in December, perhaps 50k in 2009. Far more than my normal 10-14k a year. I knew I needed to maximize my miles.
I scoured the web and discovered FT and read about the various programs, the nuances and the realities. I decided to fly with AA and did a PLT challenge.
As fate would have it I flew over 135k miles, built up a hefty stack of miles, burned through 12 SWUs, scored several OpUps on intercontinental flights. Heck, I even got an elusive double OpUp (Y-J) on BA flying JNB-LHR.
Point is you have to read FT and ALWAYS read your programs rules. Read over the T&Cs when booking.
FWIW I may fly 5 k miles this year.

(Not counting an award trip to HKT, up front on CX later this year.)