Keep it separate. As Bill the Lizard pointed out, a lot of times users might think that "+15 is already enough". This is particularly true for the type of questions asked by new users (the ones most likely to not upvote when accepting an answer)... pointingPointing out for the millionth time that someone's not using the correct operators shouldn't entitle me to 25 points... inIn fact, the easiest questions are already the ones generating the most upvotes as everyone feels qualified to agree.
I feel that one of the structural weaknesses of SO is that the way that rep is awarded rewards users who cherry-pick easy questions and rely on the laziness of voters who will only bother voting for answers that they can validate in 10 seconds or less... automaticallyAutomatically awarding an additional +10 seems an unnecessary reward (at least this is my experience in the phpPHP/jsJS/cssCSS tags where there are lots of inexperienced users)... thereThere are a lot of technically correct but uninspiring answers, and providing even higher rewards for answering large numbers of simple questions provides exactly the opposite incentive that we should be aiming for... correctCorrect answers are rewarded well enough and can always be upvoted if the OP wants.