Not that I disagree, but can I ask your reasoning?
Because they defeated a credible threat. For example, if a party, through skills, avoids combat with a beholder guarding the entrance to the Lost Tomb of Chazarai and is awarded experience, and subsequently has to fight and defeat the Beholder as they flee the city, wouldn't you award them experience again?
Full experience twice?
What my DM use to do was:
If we managed a way to avoid a confrontation or tricked it so we didn't have to fight it we got 1/2 experience for that and then if we had to kill it later we got full for killing it then.
I've seen that work with some groups before. What I am debating now is what percentage to give. I gave full the first time but the escape was something they could have avoided, thus not needing to fight them again. So, too, the enemy was not at full strength when fought the second go around. I think there were some other factors I had in mind but I'm drawing a blank as I post this so I may add more later.
In the beholder example above, they don't really avoid the beholder if they still have to fight it later, they just put the fight off for a bit. How many times can you sneak past something and keep getting full experience, if any at all?
If we avoided the fight we could get 1/2 experience the first time but we couldn't earn any more experience for sneaking past it. We also weren't allowed to go pick a fight with it afterwards and earn full experience (in that case we got the other 1/2) but if we got in a fight in a different room and he came to check out or we tried to sneak back by on the way out and he noticed then we got full experience for killing him.
I tend to give out XP in an ad-hoc session-by-session way, but I'd definitely say to give them XP any time they overcome a significant challenge. I'd even suggest that you could give them MORE XP for cleverly getting around a fight than for actually having the fight. It's different if they just succeeded a single stealth roll or something - that's neither challenging nor creative play.
Just give them what feels right for what they've achieved, I say.
P.S. I'm enjoying your blog!