If you had read a few more posts on the forum, you would have discovered that steps have been taken to remove this 'loop hole' in the promo-code system (see vicm3's post above).
I don't blame DreamHost for taking this step, as the promo-code system was always intended to provide new customers with a way to try DreamHost, without outlaying too much cash. If you like the service, which you obviously do, you are expected to pay the full plan price to renew. Allow customers to continuously use promo-codes to renew wouldn't be too financially healthy for the company.
Anyway, I think your only alternatives are to either pay the full plan cost (it's worth it ) or find another host.
Save [color=#CC0000]$50[/color] on DreamHost plans using [color=#CC0000]PRICESLASH[/color] promo code (Click for DreamHost promo code details)