The Blue and pink/red cooland has a lifespan of 5(4 to be safe) years
After this and you dont change it, it will become acidic and corrosive thus making rubber brittle and also plastick brittle due to the PH level. I have seen this alot on E46's these days. My 2003 325i E46 with 180 000km had no leaks and the pipes i removed to flush still in excellent condition because I changed it when it was due.
My advice is replace your coolant every 4 years. I know they say there are some that last 5 years or even 250 000km but I wont go that far. The chances of replacing a pipe/water pump/water bottle/ O-ring is good so then just flush and add New Anti freeze
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