Think of all that has happened in this past millennium. We know that none of us will ever reach such ages. The length of our days is 70 years - or 80, if we have the strength. Moses was 120. For man 1000 years is more than a lifetime - for God it is like a day gone by or a watch in the night.
Some days seem longer than others.
I heard someone remark that Christmas Day always feels a long day - probably because for many it involves an early start, a late night and little to do. It's nothing like 1000 years though and when we look back even on the longest day it seems nothing. A watch in the night is a period of 3 or 4 hours. A sentry on duty from midnight to 3 or 4 o'clock may find it rather tedious work on a cold night but looking back on it, it is nothing like 1000 years. How different God is to man.