@jmurthy ,
I had a look at your pictures in your gallery. I don't know where you are living but perhaps in the North of US or UK? The pictures were of winter-mammals, big mammals, birds, landscapes... and your pictures are good. You love nature, animals and you will be better in photography. You are also not old according to the photo so, you can hold the lens.
Buy that lens. As simple as that! You will enjoy them a lot! Your pictures shoot with that lens will make you happy.
The decision is right. If you take photos of the northern animals than you will profit from f2.8 (in Africa I can profit it for an hour or two and then change to the smaller lens with f4-f5.6) and with 400mm you can even take photos of landscapes.
So, if you have money then buy it. If not then borrow the money and buy it. I am convinced that you will not regret. And we will enjoy your photos if your will share them.