For me, the good times (and the harder ones to get at CRT) are typical dinner hours- 5 pm until about 7 pm. You can often find CRT dinners on or at day 180 at 4:30 or 9 pm, but 9 usually coincides with the fireworks. If you want CRT for a good dinner time that is not too early and doesn't prevent you from seeing the fireworks, then you will want to be online as soon as reservations open for your trip. BOG PPO is usually still open right at day 180, but you might have to take an 8:20 or so. That is fine. You still get in with those who have 8 am reservations.
In my experience, Garden Grill PPO is significantly easier to get than Akershus PPO. I have been able to get Garden Grill PPO within 3 months or so of a trip. Never hurts to book early though.
Wow. Have you gone during September
free dining? That is actually the only time I have not been able to get exactly what I wanted when I was online first thing in the morning at day 180. I had trouble getting the Fantasmic dinner package and BOG dinner during that time period, though through persistent site stalking I eventually got them. Free dining can make reservations tough to get- especially those that are the best values on the dining plan, like the Fantasmic dinner package.
Also, for specialty meals like Dine With an Imagineer, you sometimes have to be online at 180+ at least six if you want that (if the reservations are released that early, which sometimes they are not yet and you have to stalk the site every day or follow a thread on these boards).
For my February, July, and April trips, I have not had trouble getting the restaurants I wanted at all- and sometimes I book just a few months in advance. I do have trouble getting good dinner times at BOG, CRT, and Cali Grill though.