How can one imagine, indeed. I suppose it's not like the experience we go through in life, like the aging process - which has an influencing outlook, to being quite aware of how time affects us. Time drags along or it goes quickly; or sometimes it's both, changing like the weather. The sense of how fast time seems to move, the sense of time, depends on the age demographic, even how one feels simply from his or her health condition, "oh the joy to be rid of these pains, if only, and to be with loved ones".
If I were to dare to imagine what it would be like, I would guess that with no aging process and the ailing pains that comes with it - the sense of time, say 10 years. The experience would not feel or be noticeable to 10 thousand years. It would be a whole different mindset than the conventional outlook, that is different from the minset that gets easily bored in our current world.