I think time sinks are fine as long as certain features are included:
- The amount of work is discretely quantified (e.g. kill 50 spiders on Firesday). No vague progress bars.
- The quantity done and remaining is properly tracked, and visible (so in XI, WSNM trials were quantified but not visibly tracked, leading to a feeling of frustration)
- The amount of time needed to complete the task can be estimated (if I can kill one every two minutes, I will be done in about two hours, including potty breaks)
- The reward matches the amount of time spent (killing 500 monsters for a minor upgrade is unreasonable)
- Portions of time sinks that involve other people require less repetition than portions that can be done solo
- The time sink can either be done any time, or can be scheduled for a specific time (Weather trials in XI are the worst! Day trials are less painful.)
- The quest is not a bottleneck for further progression in the game (time sinks for limit breaks or to access new areas are unfair, but fine for performance upgrades)
- The time sink is repeatable with different options depending on choices made
In other words, people don't mind time sinks as much as they know what they've done, where they're going, and what they're getting out of it in the end - whether that's the next level or a new piece of gear. My current goal in XI is level 99 Gjallarhorn. I need to buy 5 Umbral Marrows. For that, I know I need around 70 million gil. For someone who has never had more than 9 million gil at once that's a tough goal. But since it's quantifiable, I can work toward it - I've already earned my first million gil in the last week.