Since it sounds like you are still obtaining some use from your DreamHost account, you really need to ask yourself if the service is worth the full plan price to you ? If it is, renew, if it isn't, don't renew.
The promo-code system was designed as a way to allow potential customers to try DreamHost at a fraction of the regular price. I really doubt that DreamHost could sustain their service if existing customers could renew at the discounted price.
Personally, I believe the service DreamHost provides is easily worth the full plan price.
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