They are only unreliable if you run them at 125+ whilst there pinking and then try and fix the fueling problem without knowing what your doing.

If a full day of your time is only worth £80 then fair enough go for it.

Although its actually costing you about £170 ( £80 - £250 [minimum value of your spare engines]. Its a false economy no matter how you look at it.....its a no brainer for me