In this hobby - no way, never. Well, I cant speak for everybody, but generally speaking, its an on-going process.
To a lot of people, doing the work on the car is the best part. Then they sell it, and start over with another one.
I started out with my latest project car with a big bang, spending around 4,000 in initial mods that took a couple months to install. Then I have taken as long as a year doing nothing to the car at all.
It depends on your expendable income, your priorities at the time, blah, blah, but if you enjoy modifying your car, and you keep the car for a long time, you usually will always tinker or change something.
My wife is expecting a baby soon, and unlike many others on this site in the same situation who are selling their stangs, I have vowed to keep mine, although keeping future mods to a bare minimum
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1993 GT/AOD
'93 Mustang GT