I personally feel that Indy feels the same way about himself that Harrison Ford feels about the character of Indiana Jones. Indy is just an average guy who is sometimes called upon to do the heroic. Indy probably views his heroic actions as something anyone would do if put in a dangerous/desperate situation. Indy would probably say that anyone could be a hero, really. Indy's "adventurous" lifestyle just happens to put him in harm's way more than the average person. In this, Indy probably would admit he is somewhat of a thrill seeker.
Indy does enjoy teaching, but I think he can only take so much of a "normal" life before he gets bored and begins to long for the excitement of the field again. I think this is why Indy is kind of neglectful of his teaching duties. He is often in the field, so his classwork never gets completely finished. Then, when he returns from abroad he is go swamped with work that he just doesn't want to do it-- so he, um, walks out the window in true Indy style. I think Indy considers the field part of his position as his "B" job and fieldwork is his "A" job. He does love to teach (at least, I like to think so. The novelization of Raiders suggests this), but he just teaches as his main source of income because he can't be in the field all the time. If Indy had it his way, he'd probably be globe-hopping at least 3/4s of the year.
This is a little OT, but it would make sense to me in Indy 4 to see an older Indy who still loves the field, but since he is older he is looking to have more of a "normal" life, although he may somewhat regret this. I think we'll see an Indy who has "hung up his bullwhip" and is striving to live a normal life, only to have someone present him with a challenge that will inspire him to go for it "one more time." Also, I'd like to see Indy "settle down" with a woman because I think he's more than earned a little rest and happiness of his own. If Spielburg/Lucas want more, they'll either have to get Indy a son or have someone else play Indy.