However, this feature is solely (in my opinion) to stop flooders, spammers, etc from abusing the forums.
Regulars, premium members, and such are known in the community, experienced, and if they would be flooding nonsense and spamming - then the mods would have (should have) stepped in already.
Therefor I think it's punishment for those who know what they're doing, and a bit invalid. The easy way is to of course request to have this limit per group. However, I believe a more intuitive anti-flood system might be more enjoyable.
I am thinking of say, a grace-% for those over x, y, or z postcount, for certain usergroups perhaps. So those who are just active, helping out a lot on sites, writing and replying to newbie content, and what not, don't get bothered ~much~ by the x seconds flood limit, but if there's a second or two left to go, and they qualify, the grace % would not complain to them, and give them an exception. To avoid abuse of this, the % gets added to the next post, or at least reset it to the normal time. This should catch the flooders still, but those few times you are just a second away - the system smiles at you and lets your post go through.