Why even replace them if you don't need to, especially with cheepo rebuilts. If it's worn then obviously replace it but if just the boot is split and leaking then replace the boot. Anything more is a waste of time and money.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold