Fully agree with Sheeny's comments. A few more:
Roughly speaking, at 40° altitude you are looking through 1½x as much atmospheric murk as compared to straight up (90°), at 20° about 3x... not just instability (seeing), but also light-scattering particles (dust, fine mist etc) You don't always have a choice (currently Mars comes to mind) but with faint fuzzies it pays to work out when they are closest to culmination, and observe them at the optimum time.
If you do not like planning but instead enjoy roaming the skies, try to point your scope a bit higher up, for example, have a look at the region around Sirius
Likewise, if you want to see how much you are missing by not being fully dark adapted, put it to the test, at least once - sometimes I pull an inverted black Tshirt over my head and it does make a difference... make sure you keep the mozzies out though
If after the 'test' you decide you can't be bothered - fine, but at least you'll know the difference
