I doesn't matter if you have a 1/1, 3/1, 5/1 or 7/1 ARM. You have to look at the amortization. Also you don't have to use the historical example. We use the "worse case scenario".
If your amortization is greater than 1 year up to 10 years you could base your disclosure on 5 years. This is what we do.
If your amortization is greater than 10 years up to 20 years you could base your disclosure on 15 years. This is what we do.
If your amortization is greater than 20 years you could base your disclosure on 30 years. This is what we do.
Of course as the reg states you can disclose the actual term if you wish to. What you cannot do is use a disclosure with a 15 year amortization for a loan that will have a 25 year amortization.
Here's an example of one of our in-house ARM disclosures.
* For example, on a $10,000 180-month loan with an initial interest rate of 5.500 in effect in January 2016, the maximum amount that the interest rate can rise under this program is 6.000 percentage point(s), to 11.500 percent, and the monthly payment can rise from an initial payment of $81.71 to a maximum of $105.85 in the 61st month (5 years, 1 month). To see what your payments would be, divide your mortgage amount by $10,000; then multiply the monthly payment by that amount (for example, the monthly payment for a mortgage amount of $60,000 would be: $60,000 / $10,000 = 6; 6 x $81.71 = $490.26 per month).