I'm qualifying for both FTL in M&M this calendar year and A3*G (by April 2019). After two FTL qualifying years back-to-back, I won't have to worry about it again for a while (expiry in Feb 2022), so I can finally concentrate everything on A3. I'll still be flying mostly on M&M airlines in Y but once you have *G it's quite easy to keep (12K with 4 segments).
Apart from the low earnings in LH/LX/OS/LO that others have mentioned, be aware that if you bid for online upgrades on LH you'll normally get P class, which credits zero to A3.