If you are not booking your reservation after the 180 day mark then the hot dining times even at less popular restaurants will get booked. Your best bet is to make your reservations with the assumption that your whole party will be going. You can always show up to a reservation or take people off a reservation BUT you will find great difficulty in adding people. So book what you want now and modify later if you have to. The longer you wait the less options you will have. Think outside the box with your timing. Maybe you have a late big breakfast so dinner can be on the earlier side or if you get a later dinner reservation it might just mean grabbing an afternoon snack. I planned a NYE trip 2 months out and was able to get many reservations by stalking and being flexible with my times.
Most of the time I don't think they hold and open up reservations later.
I’m booking around 6:30 am on Day 180 each morning. I have yet to get a 5:30 reservation for H&V, Crystal Palace, TRex cafe, or Sci Fi.
I’m not new to Disney or booking restaurants there. I’ve never even booked this far out in the past and haven’t had as much trouble as I’m having now. It’s frustrating to do it the right way and not get what I want.