Precise estimates in my opinion are a farce. I found myself ritually padding my estimates by 20% just to add in a bit of time should things not functions. In some cases, this bought me time I could use on my own projects are just checking out the scenery at the companies I worked with (I love women). Other times, it bought the time I needed to complete what I did and fix unexpected problems which arose.
In any case. For personal projects and 'the engine'' type projects - things like Operating System work - having no estimates works out perfectly, right? With no deliverable other than increase performance and make the thing 'more fun' for you and others to drive and/or work with, it works out well.
If I were running Microsoft, for instance, I would throw some developers and pay community members to support prior versions of the OS - by tweaking and playing with what they want to - the goal of 'having fun' and working with community members - and convert incremental updates into a monetized subscription based revenue stream based on 'best of' releases' and services that can be offered for it. And ANYTIME I saw a new area to shift into with a truly revolutionary OS model - Virtual Reality offers precisely this game changing model , that's when I would throw my development staff into developing a new OS, and work with the community to plan out an upgrade path. This evolution would most definitely require deliverable dates and estimations, for the simple reason the community may be committed to the change.
Outside of Operating Systems though - for a real tangible deliverable. Estimates don't have to be evil. But they do make it easier for others inside and outside the organization to 'play nice with developers' - particularly in team based environments where there's clear dependencies.. Not only that, when dealing with customers, it's especially nice to have a solid timeline established for alpha/beta and release versions so the PR people talking to the community don't find themselves backtracking because of poor time management decisions..
It's a clever balance, right? But in my opinion, as a homeless guy I can easily function without dates and times because - let's face it - no one depends on me nor does anyone seem to really care. Now I burned out of IT because of mismanagement - I blame mostly myself. I am actually working on my own development project - and have created my 'realistic' personal development estimate to 7 years for development completion.
Now if I was dependent on money, which I am not and don't care about it anymore, or if I had any external pressures - that time for production might actually shorten. but now that i have 'all the time in the world' and NO financial responsibilities nor desires to enter the madness of the corporate world again, I can develop this project on MY timeline.
But to be sure. I STILL have dates and times for my own deliverable. To function without personal dates and times is an exercise in insanity in my opinion.