How does a thread like this degenerate into a back-and-forth on nothing more than semantics?

First off, be aware that "account activity" usually means earning something or even specific gaming activity, so you should check the T+C's to make sure. This is in contrast to most airline/hotel programs where any type of activity - even redeeming - constitutes account activity.

As a general rule, points used for rewards expire in 12 months / one year if there is no account activity. This is true for Cosmo Identity [Identity T&C D.2], V/P Grazie [faq], mLife members who have any status (i.e., Pearl+) [mLife faq], and Boyd Gaming properties [Boyd (pdf)].

The big exceptions are CET [faq], Penn Gaming properties (recently took over Tropicana, and also own M Resort) [Marquee Rewards faq], and for mLife base level Sapphire members (i.e., no status), where points used for rewards expire in 6 months if there is no account activity.

At Wynn, points expire in 12 months regardless of account activity, although I can't seem to find a public link to any Red Card T+C's... .

Points used for rewards must be distinguished from points used to gain status levels. Some casinos use a rolling 365 day period while others use a fixed year (and I think some locals casinos use two half-year periods). Also be aware that the qualification periods have changed for various programs in the past (e.g., mLife once moved from rolling calendar to a 10/1-9/30 calendar), and what counts for status and what counts for rewards varies heavily from program to program, so it's important to check the specific T+Cs.