As Jeff noted, it may not be in your best interest to refinance now if you're seeking another ARM. If you're seeking to lock in a fixed rate (at probably where you are now on your ARM) then you definitely should consider pulling the trigger now. Many of my clients now are doing this who plan on keeping their home for a long time. Who knows what kind of inflation will come after such a long period of long near zero overnight lending rates. The feds will have us believe that they have it under control and can prevent another hyperinflation run like in the 80's. I'm not an economist so I can't comment on that but many who were around or heard horror stories from their parents about the 80's aren't taking chances. The ARM to ARM game can be very financially beneficial; you save more money if rates stay where they are for an extended period of time, on the other hand, you could get burned badly after the next arm reset. I'd make sure you know what your ten year plan is before pulling the trigger. Also, if you go for a 7y arm, you might as well consider a 30y fixed, the rates aren't too different.
Additionally, if you want to do a little digging, you can find your index type for your ARM in your mortgage paperwork from when you purchased your home/refinanced last. It's a safe assumption that your arm is a LIBOR arm but it's possible it may be another type of arm. (Your mortgage note would say this, either on the first or second page). If it has a COSI or COFI index then you may be pretty safe riding things out for 2-3 years. These types of ARMS carry a greatly lagged hike in your index (arm adjustment rates are calculated by your ARM's margin + index = rate) which means it's possible for you to be paying based on rates where they are now in a year or two (depends how lagged it is). If it's a LIBOR arm, your risk of exposure goes up significantly since it's a 'leading' index, that means that as soon as rates spike, your ARM's rate will spike if it's not in the fixed period (or immediately after the fixed period ends, it could jump significantly).
Talk to a loan officer who's good with the numbers who you trust to help you determine what's best for you based on your ten year plan.
Do a little research and plan carefully! Good luck!