I think that the lonely limit is your imagination ;)
That said, portals are usualy needed to show only SOME records of the whole related table...
It can display ALL, but to do such thing isn't better to go to a layout of the related table ?
That's good news, so i don't have to rush to make any changes!
Yes I suppose it would be more presentable to only have a selection of all the records displayed in the portal, I will consider that.