I apologize in advance if this is a redundant question, but a Search for the relevant words returns 100+ pages of results that mostly contain the word "commercial" in a different context.

I know Commercials are 29.5 or 59.5 seconds long, typically need a place at end for a tag line, etc.
And, things can be re-arranged as needed, if a piece doesn't match a particular commercial's story line.

Is there a relatively standard format used when not actually writing to picture, that makes the music generally more on target?

Thanks!

There really isn't a standard; some production houses want digital black by :30 or :60, others want music out at :29.5/:59.5, and black by :30 or :60; still others want the button exactly at the end and don't care if the reverb ringout goes over the limit, cuz if your audio is going to post, they can always fade it down. If it's not specified, it's good to ask.

Thanks! I assumed as much - I was just checking to see if anything is a dominant as the verse-chorus (Etc) structure used in songwriting.