I'm like you Wooster, retiring at the end of November and thinking it's now or never for big equipment expenditure. In my case this is also predominantly a big lens. I'm physically fit at the moment, so I'm going for it - you only live once!
That was my philosophy when I ordered this lens. It's now or never!
I've had a wobble or two but I'm reassured as the store are really good and I've used them a lot so they're pretty relaxed about returns if it really doesn't work out. I'm definitely going to try my best though as I've lusted after one for years.
Yes, sell it to me if you don't take to it!
It's a serious bit of kit and good luck to you.
To be honest if I'm speeding that kind of money on a lens it would have to earn me some money!!!
A cheaper option and often better one is to invest in a pop up bird hide and use a fast shorter lens
But I don't blame you for splashing out. It's not too heavy really