It's very interesting that 1st Corinthians 15:53 has been cited in the Watchtower study articles last week and this week.
That Scripture, speaking about humans, translates the Greek word 'athanasia' to mean 'immortality'. Can that be correct? The reason I question it is this - according to the "given understanding", the Greek Scriptures were written primarily for all those with the heavenly hope. OK, let's go along with that thinking just for 5 minutes. The term "everlasting life" (Gr. aionios) appears 46 times in the Bible - all in the Greek Scriptures.
If immortality was what the writers (as well as Jesus) had in mind, then they were all pretty negligent in their use of the Greek language by not revealing such an incredible condition being promised, that of being immortal!
The Reference Bible footnote correctly states that 'athanasia' literally means "deathlessness". (notlife within oneself) The hope held out to everyone exercising faith is exactly that - DEATHLESSNESS.
Death will be no more (Rev. 21:4); the last enemy, death is to be brought to nothing (1st Cor. 15:26); death & Hades will be hurled into the lake of fire (Rev. 20:14). No more death - deathlessness!!!! Vine's Expository Dictionary states that 'athanasia' "suggests the quality of the life enjoyed"
Why would Jehovah give immortality to some who remained faithful for 70 years, but wouldn't bestow that privilege on angels who remained faithful for 6000 years in the face of Satan? Every person who survives the Great Tribulation should also qualify!
There is absolutely no reason or justification to give anyone immortality - is everlasting life not enough?
p.s. Think seriously what happens if you change this and other verses, where "everlasting life" is promised:
(Matthew 19:16) Now, look! a certain one came up to him and said: "Teacher, what good must I do in order to get immortality?"