Maximizing the Dolphin

Part of the cynic in me knows I'm about to see a side-by-side with Opus 4.6 on categories where Qwen 3.8 27B aces it. Im confused whats the point of running /clear vs starting a brand new session. At least with the latter I have session history, no? Pardon my ignorance since Claude isn't my primary driver. How does this work on a task while I'm busy with something else and come back later I've doubled my cost because the cache expires too quickly?