Trigger betting - thoughts

[O'Brien]

What are people's general ideas about when is a good time to submit your trigger bets? Has anyone found, for example, that submitting them 1,2,3 or how ever many minutes from the race sends them into the best market? Or, are you better waiting as long as possible? Obviously, the best price obtainable is the goal, and each individual circumstance & horse will differ, and as everyone knows a price fluctuates depending on supply/demand for that horse, eventually settling on an SP, however what are people's thoughts on trying to weigh in at the correct time?