Recently changed from the SMH10 to the 20s. We're regretting it a bit. My wife's unit is frequently turning itself off. They've released 2 firmware updates since purchase and the issue still isn't sorted. There is a big thread in the Sena forum with many people reporting the same issue.
There seems to be no pattern. She's had the issue when we're out together, when she's alone on her bike, with GPS playing music and without. Sometimes it's a couple of times in 5 mins then OK for a couple of hours, others it's more spaced out and regularish in frequency.
It's a shame, as we found the SMH10 to be rock solid and really reliable. We went to the 20s for the multi-tasking and slightly increased range.