If you're in a deferred position when a block is found, the HERP is added to the next round - and it can effectively double the herp by doing so. If you are in the top 100 with the added herp the next time around you're guaranteed to get paid. If not, you will be in the interleaved group.

All of this shows you are much better off sticking to the one address. You'll get paid more regularly and are more likely to get the full payout with each block find. Additionally it means other miners get a look in sooner so it is nice manners to do so.