Evenflo Triumph?

We are looking for a convertible car seat for our 20 pound almost 10 month son. I am really leaning toward the Evenflo one that goes to 50 pounds. I was just wondering if anyone has any experience using it for an older child and just how long it will last. Or will I have to go buy another car seat before he can be in a booster. I know the Britax go up to 65 pounds but I don't really like the looks of them for the cost and they don't seem to hold anyone bigger by the size of them.