Others may have had other experiences.
Where are we talking about? Here is the best winter, in Paris it seemed to be spring, somewhere is summer.
When hive is full, it needs more space in every situation. If bees come out and are hanging outside, it is the last sign: More space.
If you have 2 boxes, often it seems that hive is full, but when you take upper away, the lowest is allmost empty.
If you are getting good honeyflow, and you see that there is space enough, you just put more. Have you there honeyflow, or is it snow fall like in Jerrymac forecast.
It is imposible to give advices if you do not know the whole situation.
To put more space is not so dangerous, but if you do not give, hive swarms.
It is most easy to look inside and see, how much hive has space. That is the way how beekeeper learns.