Fair comments and off course people are entitled to vote whenever they want - voting will be open for a fair amount of weeks.
Voting has always been open from around mid to late in the series and really it comes down to how busy the forum is as well. When the series and CBB ends, the forum dies a death and therefore getting anywhere near a good amount of votes would be a struggle.
Therefore as with every other year in the past, the voting will be open before the end of the series and people can wait to vote if they wish to in order to see if their opinions change or if anything major happens.
Personally having watched HMs for 4/5 weeks I can usually gauge where to stick them on my list.