I think it would be a very useful training tool to have auto laps by time.
I have a FR 955 but this could be implemented for all Garmins. I also have a Polar Pacer Pro which has automatic laps, which are separate from manual laps using the lap button, where I check my 5 minute average heart rate. I find this much better for managing a constant effort and also time is 100% accurate vs. distance which can vary a lot, especially in poor signal areas.