Optimization is the process of tweaking a website to get better rankings. Like tuning an engine to get a faster time at the track. The faster track time is the goal; engine tuning is a means to achieving that goal.
Same with optimizing a web site. You optimize to get better rankings.
For speed, seems that tuning for time could fall more into Google's computing speed, a searchers connection speed, and therefore the size of code and images on a website. Like using CSS and HTML would help speed for loading time, versus a big Flash file. Or, using 50K of images versus 300 K of images.
But I suppose your analogy works in one way of thinking, although I've thought of the optimizing more like as attaining a status, than a race for a finish line.
It is true though, that optimization really can't hurt. If done right, it rarely will lower a ranking spot for display. And it won't make a site harder to find.
I've still been amused by one landscape designer website though. One of the oldest websites in Oregon for the landscape or tree trades. The tags are only half what they could be. The images have no alt tags, and there are hardly any inbound links. Yet for 5 years at least, that I've looked at it, its in the highest slots.
The reason I've watched that site, is because its one that may offer some insight as to how much weight Google puts on the age of a domain name. And my estimation is about 20% worth of importance.
There's been a lot of landscape contracting companies really pushing for search results the past couple of years. And last time I searched "Portland Landscape", they landscaping companies still had not bumped that designer off the first page of search results. Although, it did finally move down about 3 positions last autumn.
I'm not even sure if the designer really needs the site anymore. But one thing is certain. If she quits the trade someday, and doesn't care for web presence anymore, that URL would be rather valuable for someone in landscape design to acquire, if the site-age factor is real. Especially if a new owner of the URL would make a few fine tunings as you call them.