We are planning to extend session to 7 x 24h instead of current 2 x 24h. Option to destroy session manually will still be there.
Glad to hear that as there are some cases people forgot to extend the session after 2 days, it's not Chipmixer fault though.
Moreover at a current mempool condition which causes most transactions stuck for days if we do not pay adequate fees.
Well, we are waiting for this feature to be implemented.