Get a second opinion from an automotive HVAC shop. I believe BMW still uses piston compressors that must be loaded frequently in order to oil the shaft seal. My VW compressor was a scroll-type still functioning perfectly after 13 years.

Heating? My X5 has an 1000 watt electric heater service until the engine has excess heat for the cabin.

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Believe nothing read or heard without verifying it oneself unless it, Weltanschauung congruent, fits ones worldview.