Originally Posted by
monvoyage
I would just say that in April Lisbon airport was considerably busier (even at 5:30am) and therefore much slower than I had expected. This was not sue to any strike or work slowdown on the date I was there. Also not laid out particularly well. 1.5 hrs would be tight. That said, it's more worth the risk on her way TO Italy than on the way home, because there will be more intra-European flights that she can be accommodated on if she misses the connection. Going back home, she likely has fewer TA options and if she misses that, it may mean extra stop(s) or waiting until the next day.
5:30AM to 8AM is the busiest time at immigration - you have redeye flights from Africa and the Americas all landing around the same time and the immigration hall turns into a zoo. The next batch of non-Schengen flights land around 10:30AM-noon but it's much quieter in comparison. The third, even smaller, bank of non-Schengen flights is around 3:30PM-5PM.