When is the future perfect progressive used? I am trying to understand in which cases it should be used, but I cannot find any practice examples of sentences using that tense.
I will have been loving.
First, just a little preface:
"I will have been loving" is an awkward example because we don't generally use any of the progressives on stative verbs (except under special circumstances). Thus, we don't normally use the progressive for things like "love", "be" (in the sense of being, rather than behaving in a certain way), "think" (in the sense of having an opinion), "have" (in the sense of possession), and so on.
Now, as for the future perfect progressive, it is used to compare two things happening in the future and how they relate to each other temporally. One event (in the future) is ongoing and another event occurs during the first one.
Let's say that tomorrow you will walk your dog from 7 - 8 AM. Let's also say that I am planning to meet up with you at 7:30 AM. We can express a relationship between these two events by using the future perfect progressive:
When I meet up with you, you will have been walking your dog for 30 minutes.
This means that, at the time of the second event (when I meet you), the first event (you walking the dog) started already and continued for 30 minutes. (It might continue for longer, though it is not required to happen).
"As of this fall, I will have been attending college for twelve years," wailed the hapless grad student.
Situations to use the future perfect progressive are unusual but not unheard of. You just have to look out for them.
The future perfect progressive tense indicates a continuous action that will be completed at some point in the future.
Next Thursday, I will have been working on this project for three years.
The funny thing about this verb form is, that you put your reference point into the future, while at the same time you are talking about the past. Only that this past is not necessarily the past now, but might also be the future. Now. But not then.
Confusing? You may can visualize this:
First, perfect progressive:
|start of event......time passes....*now* This has been V-ing for quite some time now
Now, we put our reference point into the future:
|start of event......time passes....*now*.......*then* This will have been V-ing for quite some time then
Things can get weirder, though:
|...*now*....start of event...*then*
You still change your reference point, but the start of the event also lies in the future. However, relative to your new "now", it is past. And all with just one little word...