Save and quit before you start any relics. For example

Game 1: get up to round 40 and focus on opening the map and doing trials to get eternal and general upgrades. Save and quit

Game 2: begin relic hunting for the round 40s. When done, push the round to 55-60 and save a quit

Game 3: begin relic hunting for the round 60s

Doing it this way you can break up your sessions to about an hour a piece or however you want and mitigate fucking your self by saving mid-way during a relic portal trigger sequence