I spent...
Question- Is there a "right" decay time for a given room size?
NO, we all have rooms to listen what the industry have produced for us. And the industry have standard rooms with specified decay/reverbation times.
To hear records correctly, your reverbation times at your "listening" room have to be shorter to hear what the combination of record and sound engineer have stored on the CD or whatever storage medium.
So for listening room you should be in the range of 250 to 350 ms (milliseconds).