No way to archive at this time. However, there are a few things to look at.
First one. Since you haven't noticed the slowdown but he has, then it could be related to unread posts if you have full post tracking turned on. If he only visits certain forums, and leaves others unread, then this can contribute. Have him mark all posts as read and see if he notices a difference.
If it's just generally slow for everyone, and this is your own server, or a vps, then you could look at tuning/tweaking your mysql server config. Recommended tool to do this is
mysqltuner.pl