Really thinks for all reply and comments.
Some of you are so sweet
and others kindly pointed out the problem.
Please let me explain a little more about my case.
1. Recent year, for sure I have abroad mission plan (eco mid + long 3). Clearly, it is not paid by myself. This helps me for the XP. Detailed will be negotiated later with my company.
2. I have my own travailing plan, and for sure, in the rest of my life, I will travail.
Plan 1:
Just buy low-fare ticket (Rynair, easyjet...), whatever which company. But pay for the luggage, etc.
(Maybe) cheapest option. Miles is meaningless.
Plan 2:
Keep flying with Skyteam, and lost the status one day.
I need to pay for the 2nd luggage, even 1st in Europe.
(Miles used to purchase ticket for my families).
Plan 3:
Get PFL, and fly whatever I want. Always benefits the advantage (and some hidden benefits).
In this case, I do not need spend a large mount of money.
For the plan, with all the "skills", it is fine with up to 2000 euro.
I mean it is an investment for the rest of life, maybe one year things come that I can now fly for some reason.
I totally get your guys' points: Do not waste time and money.
I agreed before I knew those tricks.
I now have been to almost famous Europe countries.
If I can (1) keep my travail habit for fun (2) reduce the trip times (3) spend less and gain more, why not?