who told you to veg that long? obviously you can but your right the longer you veg typically the larger the plant it going to get. Also can depend on your lighting in veg. If you have good lighting in veg i find 4-6 weeks is plenty. But again its all on preference.
2 metres? what size pots are they it? I'm guessing its a Sativa plant so you're looking at what 12 weeks flower? You're gonna have great yeild off a 6footer