Boston is a seasonal cruise port, with some activity in spring, lots in summer and fall, and virtually none in winter.
Bermuda is a spring / summer / fall destination. 7 nights is the most common length, but 5 and 6 night options are becoming more common. These cruises often stay 1 or 2 nights docked in Bermuda. These overnight stops are relatively rare treat, especially among the mainstream cruise lines.
Canada and New England is a summer / fall destination. A typical 7 night cruise that returns to Boston won’t get much further north than Halifax but a one-way will normally end in Quebec City or Montreal. Slightly longer cruises (11+ nights) may make it to Quebec and still end in Boston.
At the end of the season, cruise lines reposition their ships to warmer waters. These repositioning cruises often have interesting itineraries that call on a number of Caribbean ports but are usually at least 10 nights long.