When i say "more then 4 addons is maybe to much", i mean 4 big dl for only 1 mission. If it is a campaign i guess it's ok to have several more.
And in the end, like macguga says, if they're really worth having, i will dl them in order to play a mission or a campaign.
Some of the addons i like best, i only got to know them because they were used on a mission i wanted to play, so lately i just go and get them.