They're fairly predictable in that they'll always occur at the end of the debate. Some debates do progress more quickly, although they have a maximum time limit, say, of two hours. If it's something there's general agreement on, it may only take an hour and a half. There will always be a whip from each party present in the House ready to vote at any time. The only exception, as I said, would be those very small parties of just one or two members who are not able to maintain a continuous presence in the House.
On May 17th, 2016. See this statement in context.