Aside from from arguably one figure, vice presidents in the early republic had little duties aside from presiding over the senate and occasionally casting a tie breaking vote (which happened more than you would think due to the small number of senators). Many didn't even participate in cabinet meetings and were virtually ostracized within the administration. Several vice presidents in fact either resigned their positions or sought to win election to another office, Daniel Tompkins ran for governor of New York and John C. Calhoun resigned to become senator. There are many accounts of vice presidents noting their extreme boredom, some became depressed, and others became alcoholics. In addition we should remember that in the early republic the government met less anyway. In short vice presidents had plenty of free time, probably too much of it. The other thing I would note is that Jefferson didn't do the much harder role of attempting to guide the legislation through the state house, that function was left to loyal political followers in classic Jefferson fashion, in this case Breckenridge.

Edit: I probably should note that Adams had offered Jefferson to essentially be co-president with him, however owing to a variety of reasons Jefferson declined.