I'm using the "workout mode" with a lower target around meals and at other times when I want to manually encourage more insulin delivery. I use one or two hours as the duration but will turn it off early if I see a falling trend.
This morning, for example, I woke up around 60 but could see that I had not been in hypo territory for more than 20 minutes or so. For a few weeks my morning pattern was to wake up in the low end of my range, 70-99, and my BG would first head slightly lower, then over the next 30 minutes or so head higher. I've referred to this secondary rise and attendant insulin need as my "feet hit the floor" morning insulin requirement.
I've been eating one half to one full glucose tab to treat the half-hearted low and when the BG starts to ramp up, I'll use the workout mode with a lower target (I use 65) to mitigate that rise. Here's this morning's trace.
I ate one glucose tab just before 8 a.m. and then turned on the workout mode, 65 target, for one hour, starting at 8:30 a.m. when the line started to rise. I was able to stop that rise at 100. Without this tactic, I know I would have gone to the 130-140 range.
I normally eat a late breakfast, around 11 a.m. Around 10 a.m. I'll turn on the workout mode lower target and set it for two hours. This helps blunt my post meal rise to the 120 range, instead of the 140 range.