I can create a counter table (via cqlsh) with a default_time_to_live:
CREATE TABLE IF NOT EXISTS metrics2(
PRIMARY KEY ((time))
) WITH default_time_to_live=10;
Upsert a row that increments the counter:
UPDATE metrics2 SET value=value+1 WHERE timestamp='2015-01-24 10:48 -0600';
Wait 10 seconds, and select, and the row is (of course) still there. There should probably be a warning or error preventing the creation of a table that has both counter columns and a value set for default_time_to_live.