Depends on your goal. On a reach it is fastest to sail directly at your goal (as adjusted for
current, leeway, and such). A
race crew will of course trim thru the puffs and lulls. A general
rule is to trim for the light air and suffer thru the puffs.
If there is a gybe in your future, because you are sailing high for best downwind speed, or comfort, or something, you can maximize downwind speed by bearing away in the puffs - and likewise heading up a big in the lulls. This can somewhat reduce the need for trim changes, keep the
boat steady, and provide some sailing fun. The apparent wind may, or may not, stay put during these course changes as that depends on the
boat.