You freeze before better crystals
More warmth can turn a short climb into a route that reaches better crystal spots.
Mine a Mountain Warmth Guide
Warmth matters when cold stops the climb before your pickaxe or backpack can create value. Use it to reach higher crystals, not as a blind first purchase every time.
Upgrade timing
When warmth is worth buying
Choose warmth when survival is the bottleneck. Hold it when mining speed or capacity is clearly costing more time.
Mining is the slow part
If you survive long enough but crystals take too long, pickaxe speed may pay back sooner.
Capacity ends the run
If you leave because the bag is full, warmth will not solve the main problem yet.