Mmmmmm, you could have opened a can of worms here Wassy.
There are many different aspects of biking to consider when it's comes to bike change time.
Are you physically fit
Do you ride with a pillion
What kind of riding do you do ie A , B , or C roads, or are you happy to sit on motorways
How many miles a year do you intend to ride
All of the bikes that you name are huge, heavy bikes . So will be heavy on fuel, heavy on tyres, and bulky bikes that need lots of muscle to manhandle.
My experience is of owning smaller light bikes to start my motorcycling career. Then gradually , moving up to bigger bikes, but then as ageing becomes a factor, I am now sliding back down the scale, and am currently on a MK3 Versys 650. And fully expect to slide further down the scale as time goes on.
I have practical experience of the GTR 1400. I owned one for about 12 months, and must say that I didn't enjoy it. It was too big, too heavy, and didn't do anything that lots of other ( cheaper ) , and way lighter bikes couldn't have done. And the 1400 cc engine was a major disappointment, as it always seemed to revving too high , and just didn't behave like a 1400 cc engine should. I suspect that variable valve timing played it's part in that. But all in all , a big let down.
The big Triumph Trophy, are again a big (top ) heavy bike . I know 3 people that have owned them, and none was kept longer than 6 months.
The Guzzi. I have ridden on test many times, and actually liked them a lot. However their reliability record is not brilliant, and they can be a money pit.
BMW. Never fancied one, never owned one, never feel like I have missed out on anything. They are just not for me.
So, think long and hard, don't act in haste. Get it wrong, and it will cost ( lots ).
Think !!!! do I REALLY need anything that big and weighty
Is there something in the mid weight cubic capacity range, that will do a better job for my needs.
But whatever you choose, make sure that you get a good long test, and if you do carry a pillion passenger, make sure you take them on the test with you.
Good luck with the search. Geoff.