[davidsiems]

While this article makes a good point (don't say no just because you're lazy) I think it misses a more important one.

Time is incredibly important for projects operating with a schedule, especially if there's a fixed amount of development time (maybe the company runs out of money in six months).

As the implementor, it's up to you to judge how long something is going to take. Any time spent doing feature X, takes time away from tasks Y and Z. If the schedule is full(ish) then you need to have a discussion about tradeoffs. And quite often, even though X would be awesome, Y and Z are vital.