Them thar winglets only give you a significant fuel saving at cruise speeds and altitudes where the induced drag is reduced by them. On the detrimental side you have to cart the winglets up to that altitude first, and each weighs in at a couple of hundred kilos.
So: for short hops, the cost of bringing the winglets up to cruise level will outweigh the cost saved in the short cruise phase of the flight.
Regards, OORW