CS Lewis said time would probably continue in Heaven...But how?

(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.