As Midnight Season 1 comes to a close on August 11th (12th for EU), there are a couple of currencies you should, and a couple you could, spend before the maintenance starts.
Timelost Saddle
Earned by achieving 
Midnight Keystone Myth: Season One, 
Timelost Saddle allows you to purchase a past Mythic+ exclusive mount or a brand new mount from Lindormi.
However, you only have a couple of days or even hours left to both earn this achievement and spend the Timelost Saddle. The exact time is unclear, but Lindormi will no longer offer her mounts and the saddle will vanish from your inventory. This will happen either this week with the end of Season 1 or next week with the start of Season 2.
Undercoins – Maybe?
Obtained from delves, Blizzard has a complicated relationship with 
Undercoins. They have been inconsistent across seasons, with Blizzard resetting them between some seasons, while carrying over during other seasons. With that in mind, we recommend spending them before the patch arrives, just to be safe.
This applies especially if you have completed the Delver’s Journey, as some of the rewards must be purchased from vendors instead of being earned right away. Head to the Delve Headquarters in Silvermoon to spend your Undercoins asap!
Transforming Dawncrests for Gold
If you’re sitting on a pile of Dawncrests, there is a way to transform all of them into gold if you’re an enchanter.
The video below goes over the technique, but it is very straightforward. The idea is to turn all your crests into 
Veteran Dawncrest and then use them all into low-item-level crafts. By using Veteran crests with recipes like 
Courtly Wrists, the returning items become epics, meaning you get 
Dawn Crystal by disenchanting them.
It is not the most profitable trade, as it turns 80 Veteran Dawncrests into 500-700 gold, but it is better than having your crests wiped out or whatever low conversion Blizzard might offer.
Safe Currencies to Keep
While seemingly seasonal, there doesn’t seem to be plans to reset either 
Remnant of Anguish, 
Unalloyed Abundance, or 
Field Accolade. This means that there’s no reason to spend them before the new Season.
