BS, The factory told us in VW school that the engine will run hotter at high revs. The higher revs more the cooling fan will cavitate (quit sucking air). Remember the fan is turning 1 and 1/2 times more rpm's than the crankshaft . Shifting at 3000-4000 rpm's is not shifting early . If you are shifting at higher than that like 5000-6000 rpm's all the time, your engine is going to have a dissembly of all rotating parts down the road .  Shift when it feels good but don't lug the engine. The little red lines in your speedo ,if  you have them, is econo  upshift points .
  We are talking about type-1 engines here now.