I have two wetsuits, 3mm & 5mm, both jumpsuit style suits for easier entry and exit and I use a 14lb. quick release weight belt to hold me down. I use these suits in the warmer months June, July & August but have been able to get away with the 5mm wetsuit until mid-October sometimes. Depends on the weather. I wanted to extend my season longer in the Fall and certainly start earlier in the Spring, so OBN was kind enough to "counsel"' me on drysuits. I also fitted mine with a dryglove system and a P-valve, as recommended. I was also lucky enough to find on Craigslist a DUI fleece undergarment(s) for drysuits, although there are less expensive options for that.
I was in the water last week for several hours, the water temp was 42° and I was very comfortably warm in the drysuit. I'll be in the water again this Monday.