How to determine music note durations?

I read and write music, and I have been a guitar player for about 30 years. Normally I write my guitar notation in tab. Still, I like writing my music in treble clef music notation. But my guitar music can be rather involved, and when the notes are played in quick concession, or when the music is complicated, i sometimes have a problem determining the duration of each note. Does anyone have any suggestions? Thanks.