Upon purchasing a used 2013 Trek 7.1x, I almost immediately swapped out the stock 7 speed freewheel with a DNP 11T freewheel. The lower gearing was much better for cruising down the road. However as time went by, I needed to replace my chain. After installing a new chain I experienced chain skipping. I contribute this to two factors:
1) I didn't properly maintain, clean and lube my chain
2) I waited too long to replace my chain

I ended up purchasing another DNP 11T freewheel. All is well up to this point. I'm lubing and cleaning the chain more often and using my chain checker tool more often as well. Time will tell on the longevity of my second DNP but I'm not a fan of the freewheel.