It seems this season that they will be able to keep up the momentum for much longer than last season, but I would say that it also depends how things play out for them until the World Cup starts in terms of injuries for example. If they can keep their squad together, I expect them to keep performing until the World Cup break.
The weird World Cup that is hosted in middle of season can be an advantage for Napoli. Compare to other clubs and competitors in Scudetto race,
Napoli have less international players who will likely play in the World Cup. They will have less exhausted players after the World Cup as well as likely have less injury cases when the Serie A comes back.
In their club, many players are not important in their national teams and some players are not in teams which will play in the World Cup. That is a big plus point for Napoli and if they can take advantage of it, they will likely have a break out of other competitors when Serie A returns after December 2022.
It is another reason to think this season is the one for Napoli. They have good performance and they also have support from World Cup and season schedule.
Last season they started losing or tying games out of a sudden despite there amazing start into the season. This season I guess they gained a lot of confidence on top due to the game against Liverpool. The last game in the group stage is relatively relaxed for them, which also gives them room to breath and focus even more so on constantly delivering in the Serie A.
It is the second season they have good performance and have time at top of Serie A. I believe they learned something from the past season and might improve themselves in this season to achieve something better. Their target will not be in top 4 of Serie A but the Scudetto for sure.
That is a good point that you mentioned here, but I was rather referring to the World Cup disrupting the momentum that Napoli has in the current situation. In the past one could observe at times the these breaks are also kind of a break to a certain momentum of a team. Of course that doesn't necessarily apply in any case, but it has happened in the past.
Now Napoli is totally on top of everything. At least in the Series A they seem to be unstoppable for the moment and they probably will successfully keep that level at least until the World Cup starts. Afterwards we'll have to see whether they can seamlessly continue their streak.