When I first started, I had my beers fermenting in temperatures of 70-72°. As a result, I almost always had noticeable acetaldehyde issues.
Thing is, if you let your beer ferment in a 72° room, the wort itself can easily reach a temperature of 80° (and maybe even a little higher) when the yeast is at its most active. Which is, incidentally, the same time that it happens to be creating the vast majority of the flavor compounds.
When an experienced brewer talks about fermentation temps, they are talking about temperatures of the beer INSIDE of the fermentor, not of the air outside it. So when you hear of ales frequently being fermented at 68-70 degrees, merely keeping the fermentor somewhere with a comfortable (70-72°) room temperature is actually going to be WAY too warm.
Honestly, spending $80 on a temp controller and a used chest freezer is the best $80 you can spend in this hobby. The increase in quality of your beer after introducing some precise temperature control is so enormous, that it's really difficult to comprehend until you just do it.