I'm running a Wren 44 Gold between 2 airframes each one has its own pump/ecu/harness and the turbine exchange takes less than 10 minutes (couple of plugs and a fuel line plus 6x M3 capscrews).
It's a simple matter of adding each ecu's runtime together to get total engine hours for maintenance purposes.
Just could'nt justify a 2nd turbine for 2 of my smaller jets that don't get flown that much....works out just fine no issues and cost effective!