> I wonder what it would be like to work on something that takes 5 years to make
Organic is the best way I can put it. At least for software.
The largest project I've been on started in 1998 with a software team of 3 people (me and two others) and shipped V1.0 in 2003 with a team that varied in size over the years. Max was probably about 10 or 15 people. Total team size including electrical, mechanical, manufacturing, systems, technical writers, field service, training and QA was probably 70+.
It's like watching a child or a plant grow: you have this tiny kernel of functionality where you just need something to get started, not knowing how it's going to change and then guiding it in the right direction, growing all the time, as you figure out how to get where you need to go. Pruning the dead branches and rotten fruit and fertilizing it where it's growing right.
Then finally it's good enough to take to market. Then ship two major updates each year for 10 years.
It's fun in its own way, but I prefer shorter projects. I get bored easily.