Sledge said:
So if you have a fairly high con (and hey you're a wizard with wish right? if you don't then why?) you'll have a +2 there. That works out to an average of 55 (25 for first ten levels, 10 for second 10 levels, and 20 for con) and a minimum of 40.
For the record did anyone actually fully adopt the 2e High Level campaigns book? I have a hard time imagining it as the book's author specifically didn't like the idea of such campaigns.
Of course I also have a very hard time seeing 2e as "balanced", so I could be missing the picture here.
Wish cost you 5 years. In balanced campaigns, trust me, no wizard would cast it to gain some constitution points. In my campaign a wizard would have done it to be back at Con 16 (he lost a point, so he lost 10hp), but being at Ravenloft, Wishes don't really work you know.

The other wizard plays a character with average-low physical stats, so he's not even thinking of boosting his Constitution.
As for the High-Level Campaign, when I looked at it the first time, I thought that they were crazy. Some skills seem totally unbalanced, but when you put them into play from 21st level on (and not before) they are very nice.
I've tested them.
They are nice since:
a) wizards get few skills. Well, at least they do not get powerful ones, while other classes do. Since wizards are more powerful at higher level, it helps recreating some balance between classes.
b) all of the most powerful skills, like Invicibility (you make a skill check ? good, you survive any killing/hampering magic or fight until -30hp etc), Challenge, etc are not automatic.
You need a skill check (usually starts at 4 on 1d20). Wherever you make it or miss, you lose 2 points of skill for the day (or week depending on the skill). Usually you lose points also on the Bravery Skill (or Eminence skill for priest). This last skill is a prerequisite for those "broken" skills and is not that great. So basically, to be able to use those skills a lot, you need a lot of points, and considering you gain 3 cp each level (in my campaign, being ravenloft, I make it 4 and it works), it's totally balanced.
So warriors and priests get good skills, but can't use them all right from the start. Since xp progression is hard at high levels (well, it depends on DMing, but in my campaign people go uo a level maybe once each 5 FULL adventures), it is ok.
Thieves get some new skill, some which I think are a little anti-Roleplay, but whatever, and especially Evasion (which allow thieves to dodge fireballs, meteor swarms, etc). This is surely the most powerful thieves' skill, but then, it is not automatic (you need to roll a save) and it's not like Thieves have a lot of hp (fewest besides Mage) or magic (like wizards) to protect them from this kind of evocation magic. Also, it goes alongside well with the rogue class.
All in all, in 2ed, where power do not really increase for characters after 20th level, the High-Level Campaign Handbook is a welcome add-on and very well balanced.
We're at 25th level right now, and I know that my group is always looking upon that next level (even mages, with some skills like Signature Item or Spell Sculpting) to gain some more power.