It's not about the destination, it's about the journey.
I also endlessly tweak things, including my car. What I've learned to do is to treat such things as a project, which includes a cost analysis: is it worth it for me to spend that much time to do it myself? Planning the mod is one thing, planning the time it takes to do it is another.
Once in a while though, one of my projects slips past the cost, and gets filed under "hey, it's a hobby!". It still beats whatever else one would do otherwise with their free time.
Now if I could just convince my wife that turning the garage into a machine/work shop/office is actually a good idea... :shrug: (I found a great plan in some woodworking magazine for such a building
)