I'm currently trying to buy everything and anything I can relating to the building of AR 15s. Prices won't get cheeper as long as the current regime is in power. What will happen is that parts will be harder and harder to find. If there is a second "Modern Sporting Rifle" ban, they will have learned all the mistakes they made in the first one (mistakes from their point of view) not ours. There is no best time to buy. Just buy it when you can find it and afford it.
Life member NRA