well segwit is supposedly available as of april. so if we were to make 2mb in a core relase today.. and had 75% miner consensus in 7 days of blockdata(1000) blocks.. bringing us up to march.. and then a 1 month grace period (even i have to admit thats a little short) then that would be a mad rush and still not beat segwit.

however instead of 16 months. we suggest 8 months.. then thats an acceptable amount.. i would have said 5 months because core thinks its ok to make a release in november one in march and another in april, so 4-5months seems ok to core.. but due to it being a hard fork, 8 seems more gracious.. and definetly better than 16