Peaking for "A" Race ?'s

How long does your "peak fitness" last when gearing up for your "A" race?

 My big race is August 31st so the volume of my training is being reduced this week and next. I swam yesterday morning and felt incredible, nice and smooth and swam fast with what felt like less effort than usual (there was a fair amount of rest built into the workout) total meters was 3300, then I ran after work and felt better than usual (one hour, about 8 miles). This morning I took the bike out for the scheduled workout and rode strong but it felt easy.

 I'm worried that I'm leaving my best efforts in the pool/on the roads! Last week there was some forced rest, my body and mind were cooked and now I worry about being in top form for race day.

Or are these thoughts/feeling all part of "taper madness"?