Previous works on leak-tolerating GC and write-rationing GC show that most reads/writes in an application are concentrated to a small number of objects. This suggests that many applications enjoy a clear and stable clustering of hot (recently read and/or written) and cold (the inverse of hot) objects. These results have been shown in the context of Jikes RVM, for stop-the-world collectors. This paper explores a similar design for a concurrent collector in the context of OpenJDK, plus a separate collector to manage cold objects in their own subheap. We evaluate the design and implementation of ThinGC using algorithms from JGraphT and the DaCapo suite. The results show that ThinGC considers fewer objects cold than previous work, and maintaining separate subheaps of hot and cold objects induces marginal overhead for most benchmarks except one, where large slowdown due to excessive reheats is observed.