I have never forgotten to turn because I only have auto-turn incubators but - when candling eggs, any which are dark at the top and have a clear space underneath turn out to be dead and decomposing, except once when there was a clear space all round because the eggs had dried out in insufficient humidity. (happy ending tho as I hatched them myself and saved three out of four, all girls). If you don't have auto-turn, the linking to another activity idea sounds a really good one. Better still, use a broody hen because she turns them loads and you never have to think about it.