Keep your screen awake for a task
Start with the task you need to finish: following a recipe, presenting slides, reading reference material or watching a long download. Each guide pairs a suitable timer preset with the limits that matter in that situation.
AwakeTab works through the browser. Keep its tab visible, leave the device open and watch the live status pill. A hidden tab or a battery-saving policy can release the wake lock; the pill changes immediately when that happens.