When to sell car

[car10002]

Hi

How do people know when to stop putting money into a old car and save for another one when they'd like some money for other areas as well as car but their cars costin them a lot currently in repairs how do they fix it when they don't want to let their old car go,

Currently needs a steering rack at some point and a au engine swap then aircon then should be good trying to get most if not all done soon as possible as family don't know how much work particular car really needs and if they found out they'd talk you into selling up when you aren't intrested just wondered that's all

How else do people know to start planning for another car when they done over 200,000km even if there's nothing wrong with them currently what makes people do it