(See 'Letters To Malcolm') CS lewis said, because mankind is by definition finite, that we shall always be in a situation of successive time, with the present becoming past. In 'The Problem Of Pain' he says that time in Heaven may not be so much like a linear line but have thickness like a plain as well. I'm a bit confused by that analogy as that still inplies length...does he mean we will just experience 'a lot of things' within time or, erm, well, help! Great guy CS Lewis but am a little confused on 'how' he thought time would behave in Heaven.
As I understand it, he is saying that our future perception may be "expanded", while still being qualitatively the same - in particular, not approaching the very different perception of time that God has. (We experience time as a succession of cause and effect; we can remember the past but can only conjecture about the future. On the other hand, God sees all times at once.)
In the letter, he talks about the thicker line as a suggestion that we could experience a "wider" present than we currently do, by being able to see and understand more things at once. However, we are still on the line, and so we have the same inability to see the future as we do now. This matches the standard account of angelic knowledge: angels' intellect is like our own, but better, so that they can make more accurate deductions about the future, but still have to deduce rather than perceiving it directly. In the same way, angels are better than us at noticing things and in the general acuity of their senses, but they still fall short of God's ability to see things as they truly are, as opposed to their being mediated by the senses.
Part of Lewis's thought in the letter is that the future "resurrection of the body" implies that we will have bodies (and senses, and minds) that are still basically the same as now. They are perfected, but are still not divine. Scholastic philosophers argued that our perception of time in heaven might be different for several reasons -
This seems to match the Lewis conception of the thicker line. There is still a succession of moments, but we may perceive things differently during those moments.
There are at least two solid Biblical scriptures which prove that time continues in heaven. First in Revelation 19 Jesus returns in the second coming riding a white horse, we know that at that time the saved are taken to heaven for it is written
The very next verse after Jesus return in Revelation 19, Revelation 20:1-2 says
Here we see a time element, a thousand years.
Also there is another verse that tells us that the seven day week will continue even in heaven for it is written
Herein is evidence that the seventh-day Sabbath will still be kept even in heaven. A comprehensive Christian site about this can be found here - http://www.sabbathtruth.com/
Hope that helps!