my older trees are on drip system. i only have 4 old trees. it works well on them, however, i also give water by hand few times a week to spots that drip system missed. they can go on forever on drip system. make sure the battery is fresh like deserdancer said if you are using electronic timer.
all my 1 gal pots are watered by hand. i only have about 25 of them. problem i see with 1 gal pots on drip system is, each one loses water at different rate. even tho i pot them up all at the same time, ones growing slowly with less leave will go on for much longer without the water. so.., drip system in this case might cause to water too much, unless they are on different timer.
even at over 100 degress, the 1 gal pots will go at least 3 days without water. they stay under the shade most of the day. only get sun for about 5-6 hrs.