I agree with everyone's input so far. First, it would likely be best if you're thinking about arpeggios vs. actual chords in most case, with the occasional exception for double stops (5ths and octaves). On the extensions, I usually try to understand how much of these extensions will be utilized by other instruments and in what relative frequency range. For example, it might make more sense for me to play lower notes (e.g. the 13th as the 6th, the 11th as the 4th, the 9th as the 2nd). It also may make sense for me to just stay within the familiar ground of roots, 5ths, 3rds, 7ths and octaves. If I can't work it out with everyone else ahead of time, I will tend to follow the later course as well as try to stay within the frequency ranges that are specific to bass.