While I understand the intention behind some of these suggestions, I'd personally avoid any "you can't use encounter/daily powers until X occurs" house rules. I know that, as a player, if I saw the perfect opportunity for a specific power and wasn't permitted to use it because the DM felt the combat hadn't gone on long enough--by whatever measure he was using--the frustration would far outweigh any potential benefit.
I agree with this, not being able to use an encounter/daily power when I want to would be more annoying than anything else.
I think good monster selection/encounter building could also be a less system-impacting way to fix this. If you don't now which creature is the scary one, you'd want to poke around with your at-wills, rather than wasting an encounter or daily on one that can be killed relatively easy.
Otherwise, I'd support house rules to encourage the player to save their encounters/dailies rather than forcing them to wait. Especially if monsters are able to blow through their high damaging powers from the start. It makes for a scarier fight, but it would annoy me to no end, at least.