The thought occurs to me that no matter how much planning you do or how good at estimating you are, the development is going to take however long it's going to

The thought occurs to me that no matter how much planning you do or how good at estimating you are, the development is going to take however long it's going to take. You can plan your trip to the store to buy milk and figure out exactly how long it will take, but the only thing that actually matters is that you arrive back home, with milk. If that milk is absolutely necessary, whether it takes 30 minutes or ten minutes to get it is really a secondary concern. If you spend five minutes getting a better estimate you've delayed the milk by five minutes regardless of how long it takes or how right you were about the timing. I think we spend too much time thinking about time estimation when the planning we should be doing is figuring out what is so important that the time it takes to build is worth it even if the time estimates are off.