When you say you got a new seal, I assume you are diving dry?
Cold limits almost all my dives nowadays. Here are the things I have learned:
1. Do not waste any heat before you dive. You want, if possible, to be almost uncomfortably warm until you get in the water. If that means wearing your undergarment in the car, do it. For me, it means a hat and a heavy jacket in any temperatures below 60, and sometimes above that, if there is a wind. Ideally, by the time you get the suit zipped, the cold water is looking GOOD.
2. Wear the insulation you need, and put up with the weight you have to carry to do it. I have gone through a number of iterations of undergarment, and each time I change, it seems like I have to add lead. I'm current diving the Whites MK3, which is the warmest undergarment I've found yet, but I use 31 pounds of ballast to sink myself.
3. Don't be overly parsimonious with your weight. People stress the importance of proper weighting, and that is true. But if you weight yourself so that you have to be shrink-wrapped during your safety stop, you are cold at the worst time of the dive to be that way. I want to be able to keep my suit inflated enough to loft that undergarment, all the way to the surface.
4. Use Argon. The studies are conflicting, but there ARE studies that show it makes a difference. And I know an awful lot of people (myself included) who are true believers. I rarely use it during the summer, but once the water goes below 50, it's with me on every dive. It's worth the investment in the gear required. The fills are trivial.
5. Dry gloves. They make a difference.
6. If you are using rock boots, don't cinch them down so tight that you get no air in your feet. Although you obviously have to control air in the feet, you want SOME there, or your feet will get cold really fast.
Using these ideas, I was good for three hour-long dives a day on our recent trip to Browning Pass. But I was darned cold at the end of the last one
If they ever come out with an Aerogel undergarment, I'll be first in line . . .