We generally talk about gardens as never finished, unlike paintings that are finished. I don't paint but I imagine whether a work is finished or not is an arbitrary decision by the artist. If it’s been sold or given away then it is certainly finished. But if it’s still hanging around then the artist can touch it up or radically change it at will.
It is true that a garden never stays the same. But I am thinking that there is a difference between updating the current basic design by weeding, pruning, etc. and pulling stuff out to start again. Until recently every few years I changed the garden. Not for the sake of it - although that is what a few uncomprehending friends and relatives believe – but for design reasons.
I used to be ruthlessly uncompromising. I’d see something that looked out of place or unattractive, (even a tree that was 3 years old) and within days it was out – moved, given away, even on the way to compost. (I told you I was ruthless). Now on the whole I’m pretty happy with the way the garden looks. I think twice now instead of starting again all the time in the search for perfection. (Except in a couple of spots that are definitely still unfinished!)
At the moment there are two plants in the garden that are not perfect in my design-eyes but I think I will compromise and keep them anyway.

One example of my newfound pragmatism is this Acacia itypheallea shrub. I planted it about 3 years ago and forgot to consciously withstand the urge towards symmetry. Consequently I placed it right in the middle of its garden bed!!!!!!!! I wish I would have planted it about a metre to the right but intend to live with it as it is.

The other example is this Teucronium betonicum. I have two specimens and they have both been extremely mobile, probably moving around the garden at least 5 or 6 times. Now I have found two spots where they associate beautifully with their neighbours and are growing healthily and happily.
Unfortunately I didn’t realize the flowers were such a bright pink colour, nor that they would be in flower at the same time as the wallflowers whose pink is much more subtle and muddy. I like the look of the flowers but they spoil the colour scheme of the front garden. I’m not going to move them though. I have a brilliant and simple idea to remedy this problem. I’ve decided to cut off the flowers – as soon as I photograph them to illustrate this point.