Thanks Звездочёт,

I hope that one day I will have a good enough command of this language to need to know the subtle changes of meaning, but I think that for now, maybe I don't need to.
My goal is to be able to read Russian very well, and I think that good writers use these subtle nuances of meaning between the aspects to great effect; I'm concerned that maybe I won't notice these 'clues' in their writing, and then I might well lose the thread of the story, or just fail to enjoy it...

But that's for the future, I think. There's no hurry here...