The JW's believe the scripture in Matthew 24:13 - "But the one who has endured to the end will be saved".
The end is the start of the Great Tribulation therefore they assume no righteous person will perish in between the GT and the Big A...and it is generally accepted that the time frame between the two events will be very small since Babylon The Great goes down "in one hour" (Rev 18:10).
So whilst there will be a peroid of great suffering their explanation makes no sense...if I KNOW I am saved right at the point of the start of the GT then no matter what happens I know I am safe...guess it might be different if I had a gun to my head but an old WT used to say Jehoover would stop the mechanical parts of weapons during the GT....
When I first got the "truth" I understood the Big A was salvation but some JW's might perish during the GT and the Big A but the organisation as a whole would go through but I was firmly corrected on this by an elder who stated that it was the start of the GT that signifies the start of "the end" and thus Matthew 24:13 comes into play then...
So again I repeat...a stupid idea...oh the GT will be nasty but see when it starts...if you have been faithful you are guarenteed salvation then so no matter what happens DURING the GT you will be alright.
Was quite funny, we recently had a talk about honesty and the speaker did not mince his words and said that Jehoover has no time for liars or people who cover up sins...I was still an elder at the time and a young wife who was married just a year came up to us at the end of the meeting and confessed to giving several boys oral sex in the congregation...she wanted to come clean so she could survive the GT...husband was raging naturally...