So far, I use a combination of "tactics" -- I try to upgrade before I go to bed. Much of the time, I will be out for 12 hours anyways.

Also, I have all of my gear from before getting my current gear, so I can use that. In addition, I have, on other occasions, purchased cheap temporary gear, so I know that should I desire, that option is also available.

But of course, for the really particular player, just have two sets of your equips: one set to upgrade, one to play