When we bought our home in 2003, we thought we will be moving for sure within 7 years. Hence, 7 year ARM of 4.75%, while 30 year fixed at the time hovered around 6%. Since then, we refinanced twice, both times into 7 year ARMs - 3.5% in 2009 (fixed rate was just under 5%) and 2.25% in 2013 (fixed rate at the lowest was around 3.5%, I think), all with no points or closing costs. So far, the ARM strategy has been paying off, even without moving.
Similarly, for one of the rental properties bought in 2004 with 5 year ARM, the fixed part of rate was 4.25% and then when it started resetting, it kept in falling down, to 3.25% currently, 10 years later.
I am aware that with refinancing, we have reset the mortgage countdown twice - the way I decided to combat that issue is by saving a difference between original mortgage payment and the current mortgage payment and eventually paying off the whole thing in one fell swoop on the original schedule if the rates rise too high and we can't refi for some reason. And I ran the numbers with margins, caps, etc, to see how long before 30 year will pay break even with 7 year ARM in each case, and in each case it was sufficiently long time to take the risk. It may have been even more financially advantageous to get 5 year ARM in some cases, but we were more comfortable with 7 year terms, mostly from emotional perspective, not actual hard numbers.