My washer has this 'Eco' mode, that is supposed to optimize time, water, and energy usage based on load weight and how dirty my clothes are. It finishes anywhere between 30 to 50ish minutes. Same settings an d all.
No, not at all. It's not really possible unless you're using an extremely basic washer with no spin (Or a very poor spin) cycle. A lot of the reason washers are terrible at estimating how long a wash cycle is going to be is because they spend a variable amount of time balancing the clothes before the spin cycle.