Paths and traditions vary widely in their relationship to what you might gain and how that motivates practice. Advantages of goal-oriented traditions: they tend to achieve goals. Downsides: competition, future-orientation, emphasis on maps over practice, and the like can all occur, though these can all be mitigated and even overcome if one realizes that to achieve goals in this business requires being right here, right now, as this moment is the basis of practice and everything else, for that matter. Advantage of non-goal-oriented practice: basically that there is much less artificial division that can be created between this moment and one's practice, but the downside is that many will get nowhere at all. It is a paradox, and boils down to individual tastes, goals, proclivities and how well one implements either path.
Mixing paths: it is very common these days, and I know few who have stuck strictly to one tradition, though many have spent a good deal of time in one practice to see where it leads. There are definitely some things that mix better than others, but a total ban on mixing paths is not only needless, it is very hard to actually pull off, as our conditioning these days and the concepts we bring to this tend to come from all over the place.
Going too fast: similar to the thing about goals. Really fast progress is actually possible. In general, the benefits of fast progress are fast progress. The downsides are that it can be hard to integrate, and the risk of strong side-effects is higher, both good and bad. That all said, without insights to integrate in the first place, no integrations occurs, so getting insights is good, in general. I tend to vote for fast progress if you can pull it off, realizing that it can be a rough ride and that is still takes time to let those insights permeate the vast range of our habits and conditioning.
