They built 100 launchers and kept approx 64 missiles in them, and even replaced their original missiles in the mid/late 80s. This is better than the US effort; building the PARC radar, missiles, launchers etc but shutting it down as soon as it went operational in 1974(76?) and scrapping the missiles in 1983, but not by that much.
If both sides had their 2 sites, one each at the national capital and an ICBM site, they could perhaps relax their nuclear posture somewhat to 'launch under attack' knowing that even 200 ABMs would give them valuable minutes to gain confirmation of the attack. The US ABMs could be used in conjuction with the MX ICBM as a major deterrent system.