All my adult life, I've considered that it
will happen exactly the way that you described:
1) That the two witnesses prophesy for
1260 days,
2) then the beast ascends and kills them,
3) and then the beast goes on for a
subsequent 1260 days.
That their two opposing ministries are
like bookends in time, defining a full seven year
tribulation.
But, is there any possibility that each of
their 1260 days is not back to back?
What if, instead of one of the beast's
first acts, to kill the two witnesses, is actually one
of his last acts?
I think the difference may hinge on the
word continue:
Revelation
11:7 And when they shall have finished
their testimony, the beast that ascendeth out of
the bottomless pit shall make war against them,
and shall overcome them, and kill them.
Revelation
13:4 And they worshipped the dragon which
gave power unto the beast: and they worshipped the
beast, saying, Who is like unto
the beast? who is able to make war with him?
5
And there was given unto him a mouth speaking
great things and blasphemies; and power was given
unto him to continue forty and two months.
If the word, "continue", in Revelation
13:5, only applies to continuing "after" the killing
of the two witnesses,
then
you would be completely correct in saying that the
total, then, adds up to seven years.
However, if the word, "continue", in
Revelation 13:5 is in relation to line 4,
where
it asks, " who is able to make war with him?",
apparently some will fight against,
but
utterly fail to stop the beast, then in that context,
the word, "continue",
would
show how the beast perseveres, regardless of who
fights against him.
If so, then their 1260 days are possibly,
concurrent, in parallel, rather than in subsequent, in
series.
If that is possible, then while the beast
operates, there is still a voice against him on the
earth, actually two voices.
That would be very encouraging to those
who decide not to take the mark, and may actually be
what convinces them not to.
Also, the book is not always sequential,
i.e. the beast doesn't rise twice, once in chapter 11
and again in chapter 13.
That is similar to the LORD not creating
man twice in Genesis, once in chapter 1 and again in
chapter 2,
but
rather that chapter 2 goes into more detail of what
was first mentioned in chapter 1.
Chapter 11 is physically located before
chapter 13, in the book,
but
couldn't they both be describing things happening at
roughly the same time?
e..g. does everything in chapter 17 only
happen after all those people are gathered at
Armageddon, Revelation 16:14-16?
Or do some things mentioned happen earlier
on? for example:
Revelation
17:10 And there are seven kings: five are
fallen, and one is, and the other is not yet come; and when
he cometh, he must continue a short space.
It doesn't mean that the seventh king
still has not come yet, even when the troops are
already at Armageddon, does it?