Yeah I agree about the life before an engine is rebuilt and taken off the wing but I needed some statistical information for MTBF and I found something in EASA :
CS-E510 (g),(2)
(g) For compliance with CS-E, the following Failure definitions apply to the Engine:
(1) An Engine Failure in which the only consequence is partial or complete loss of thrust or power
(and associated Engine services) from the Engine must be regarded as a Minor Engine Effect.
(2) The following effects must be regarded as Hazardous Engine Effects:
(i) Non-containment of high-energy debris,
(ii) Concentration of toxic products in the Engine bleed air for the cabin sufficient to incapacitate
crew or passengers,
(iii) Significant thrust in the opposite direction to that commanded by the pilot,
(iv) Uncontrolled fire,
(v) Failure of the Engine mount system leading to inadvertent Engine separation,
(vi) Release of the propeller by the Engine, if applicable,
(vii) Complete inability to shut the Engine down.
(3) An effect falling between those covered in CS-E 510 (g)(1) and (2) must be regarded as a Major Engine Effect.
(3) It must be shown that Hazardous Engine Effects are predicted to occur at a rate not in excess of
that defined as Extremely Remote (probability less than 10-7 per Engine flight hour). The
estimated probability for individual Failures may be insufficiently precise to enable the total rate
for Hazardous Engine Effects to be assessed. For Engine certification, it is acceptable to consider
that the intent of this paragraph is achieved if the probability of a Hazardous Engine Effect arising
from an individual Failure can be predicted to be not greater than 10-8 per Engine flight hour (see
also CS-E 510 (c)).
(4) It must be shown that Major Engine Effects are predicted to occur at a rate not in excess of that
defined as Remote (probability less than 10-5 per Engine flight hour).
λ=0,00001 failure/ 1hour=10/106hours=10FPMH
MTBF=1/ λ=100000hours