For those that like to plan ahead......
If I have calculated correctly, the total number of choices where you can improve by spending your talents, is as follows:
To put this in context, when I was near the end of the game, having completed the majority of the 'swamp cemetery' stuff, I was rated as Seasoned Witcher with 3*. At that point in time I had accrued total talents
I chose this point in the game, as things become something of a 'running the gauntlet' soon after this, until the end of the game.
What is clear, looking at the talents I had earned, is that you get enough Bronze choices to put skills almost anywhere. The slots become mostly full near the end of the game.
You are woefully short of silver choices, as I had 36 at this time, and 102 possible places to put them.
You are short of Gold choices too, but there are not so many possible choices, only 33 places to put a gold talent.
So choose carefully where you put your silver talents. Here is a little advice.
When putting talents into the various Witcher signs, I never used Quen (shield) or Yrden (pain and damage) at all. Axii was useful just a handful of times, like when surrounded by a Salamandra horde, since it could make enemies fight each other (Hex). I used the Igni (fire) and Aard (knockdown, or force back) signs all the time.
'Group Steel' style was a good place to expend some of those hard-earned talents, there are many places where you fight a human or humanoid group. I never used 'Group Silver' style anywhere near as much, though it can clear away lots of Drowners nicely. Having abilities in 'Strong' style and 'Fast' style are essential, both with Steel and Silver swords. Some big guys would take forever to bring down with 'Fast' stle, and equally, some opponents you just will not hit, unless you use 'Fast' style.