The haters will be in soon to talk about how the relay isn't needed, adds cost/weight, prone to failure.

I carry a jumper so if the relay were to fail at the track, I can jump around the relay and be no worse than the constant hot alt line method. If you get tricky, you can use a weather-pak. Also, I usually have a spare relay with me so it can be changed if necessary. Knock on wood, I've never had a S605 fail yet.