RDS in the US is really almost a lost cause.

Yes, the signal must be pretty good (in my experience). I've got one station locally that does RDS for it's call letters and a clock. The other station is located about 80 miles away, which does the call letters, clock and uses the messaging to send ads. Joy.

I have yet to hear of any of the cool features of RDS every being implemented in the US. Traffic announcements, autotuning... It'll probably be a cold day in hell before that happens here.

Travelling around the south east, I've found about 5 stations that do anything with RDS and 3/5 of them are clock and call sign only... Typically with the clock set wrong.

I've seen it come and go randomly. Honestly, I don't think that most of the stations even know what it is. Lord knows that if they did they would use it for advertising.

As to why it would show up once, but never again.... What is your typical signal strength? I don't recall ever seeing RDS on less than 1 bar from full strength.