I plan on going in chronological order, but this order is subject to change since I have many lesser ideas for settings and characters that do not necessarily call for whole plots themselves and need to be fit in somewhere. Everything is still being refined. As Nate ages, he notices that his adventures become ever stranger and he goes from saving single villages and planets to saving whole galaxies and multiverses. This is caused by a side effect of time travel known as a weirdness field (unless somebody has a better name). Thus, the later adventures have a much different flavor than the ones I’m working on now.
The Weirdness Quotient: People often time travel for the purpose of skipping boring moments and catching exciting moments they would otherwise miss. Because there are fewer exciting moments, this is why they are called weird (not normal). Every time someone does this, they send causative ripples through the universe that subtly alter the flow of history, even if no deliberate or overt change is made. Over time and after very many trips, these ripples interact with one another in complex ways to ensure that nearly every trip is exciting, seemingly by chance.
At least, this is one way to look at it. The question remains why there are so many boring moments in the first place. There exists something called a conformity field projected by all matter (and anything that can be called a thing – including ideas). This field holds the attributes of things in conformity much as gravity holds matter together in space (“orbits” are even possible). This is why so many parts of the universe are uniform (being empty), while only a few are strange (containing stars or planets). In the same way that General Relativity predicts that all closed gravitational systems must either collapse into a singularity or expand indefinitely, Weirdness Theory predicts that things must eventually either become permanently boring or else become ever weirder until reality completely shreds. On the scale of the universe, this naturally occurs in many billions of years. When someone time-travels, they in essence create a personal universe around themselves by means of those causative ripples mentioned earlier. Being smaller than THE universe, this personal universe can reach disaster in less than two thousand years (depending on number of trips and other factors).
Time-travelling makes one’s life more interesting, gradually becoming ever more unusual as the years progress according to the time traveler’s personal timeline. If the time traveler lives long enough, he/she will eventually reach the decision point. This is the point at which they must make the choice which end they will face: boredom or insanity. Once made, the decision is permanent. Things will either begin to gradually mellow out or will continue to accelerate into chaos. It is a very hard decision to make.