There are some places in the world where this could happen, an airline run on the whims of a government. Up until the early 2000s an employee at Olympic Airways meant he/she (or a relative) knew someone high up in the government. The OA pilots could make anything happen, bring almost anything through customs, etc. I picture this still happening today with LAN or a Thai, an Aeroflot or a Kenyan.
I have been given top tier in a few airlines, both US and foreign, through the respective airline's sales offices, to get my business; it is done all the time (status matching is different). One airline I rarely fly has given me top tier for the past 15 years and I have never asked if it was "for life" just in case I would bring to their attention a mistake - it allows me status benefits with a US airline I fly once in a while.
I burned a bridge with one US airline in particular when I asked if they could do me a favour and give a colleague a higher tier status, like they did for me. They did me the favour and upped his status for a year, but never spoke to me again - lesson learned.
If you are doing a private deal with an individual who so happens to be a pilot with AF, I would give it 10% chance it would work in your favour (he could be a senior pilot with the connections you need for your request). "For life" I would give it .09% and that's because anything is possible.
I can't see a situation where you would be working with an AF pilot for AF business and want to mess things up with your relationship. One of my closest friends is the president of sales for Boeing for a region and it would be in bad taste if he were to ask, for example, say SQ, to throw in "lifetime PPS" for him with their 777-300ER order.
Just sharing my experiences and thoughts. Having "burned my fingers", I would say to you, be careful, you may be walking on thin ice. On the other side, it never hurts to ask.
Good luck!