When is the preterite progressive tense used as opposed to the imperfect progressive? For example:
Estuve comiendo
Rather than
Estaba comiendo
Isn't the preterite progressive a bit of an oxymoron? The preterite shows a completed action, but progressive tenses imply that the action is still ongoing.
It is actually rather difficult to construct a context for "estuve comiendo" that makes sense. I was having trouble coming up with something, so I googled it with quotes. Here are a couple I came across. They work, but they sure aren't commonly found!
Aquel éxtasis duró todo el tiempo que yo estuve comiendo. (That ecstasy lasted the entire time I was eating.)
(I guess there was something special about that particular meal.)
Últimamente anduve estresada y a las corridas y estuve comiendo muy mal, mucha comida chatarra y azúcar. (Lately I was stressed and always rushing, and I was eating badly, with a lot of fast food and sugar.)
In both cases, we see that there was a period in which eating occurred, but that period had a clear ending, i.e. it is not going on any longer.
progressive tenses imply that the action is* still ongoing... *or was still ongoing at the moment, in the context of whatever you're talking about.
So you'd say "Ayer estuve comiendo en un sitio muy bueno" (the action is finished, nothing more to say about it) or "Ayer estaba comiendo cuando apareció Pedro" (the action of you eating was still ongoing when Pedro appeared).
