Если двигатель хоббийный (обороты максимальные до 13-14 тысяч) и не пережат ( косвенно судить можно по тому что двигатель очень редко в обратную дает) то можно сказать -вечно.
По крайней мере на одном движке более 60 часов, на другом более 20(потом моторы сменили хозяина)
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