Good idea! I plump my pipes back up every year. Keeps 'em nice and round!! :whiste:
The only concern you really should have, IMHO, is if you have trees running close to your sewer line, and usually then ONLY if you have an older clay tile sewer line. Since your house is only 11 years old, it's likely your sewer line is plastic, so you should be good to go.
I have heard that if you have low-flow toilets, they do tend to not flush the sewer line quite as well as the older toilets that use more water. However, unless your lines are split up (gray water, i.e.-sink drains, and black water, i.e.-toilets), your shower water should be sufficient to keep the lines flushed. If you're worried about it, do a couple extra clear water flushes, per toilet, per month.