Just keep my comments in the right context, guys. I'm only suggesting ways to counter a player who decides to start using massive spellburn in what he percieves to be the last climatic encounter of the adventure. And these are just a couple of suggestions, there's obviously several other things you could do to discourage it.
In my opinion, as judge I need to do something to discourage that kind of behaviour, because the only other alternative I can think of is to escalate the brutality of those last encounters so that this kind of massive spellburn doesn't turn it into a walk in the park every time. Screwing the party out of a few xp's isn't a big deterrrent in my opinion, and I don't want to start going the route of needing to create encounters based almost solely on the strength of the party like that other game. So if someone wants to abuse the letter of the rules, I'm going to try to come up with something that tends to herd them back on the path.
Look to the rulebook for a moment, because I think that this is handled. When a monster dies, it need not simply die. A monster's death may easily unleash another horror -- look to the modules for examples of this -- and some of those horrors might well be an encounter after the climactic encounter, i.e., something to deal with after
that massive spellburn.
In several Appendix N stories, the death of the "big bad" results in the need to flee a landscape that is now coming apart. The much-spellburned wizard or elf may have great difficulties dealing with that. Only if what seems to be the climactic encounter is almost always the climactic encounter, and only if there is almost always time to recover between adventures, is massive spellburn a sure thing. Make it a gamble, and players will think twice. So long as it is a gamble, it feels great when it pays off, but there is a dread of when it does not.....you should not pull punches, either.