In my context, more than a year is starting to be a bit long.
A long interregnum can be a blessing, if you use it well. It can be a time to review your church's sense of identity and mission; what do you want your church to look like in 20 years? What skills and gifts will the next person need to have, to lead you in that direction?
It can also be a time to get a lot of things in order; deal with any conflict, that sort of thing.
Before I came to this church they very deliberately reviewed the buildings, dealt with all maintenance issues etc, so that when I got here I wouldn't have to worry about a leaky roof (or the like) but could focus on ministry and mission.
So it doesn't have to be a bad thing, but it depends how you approach it.