Hi there - super paranoid and trying to get some newly purchased trees to grow vigorously. I've got figs and citrus in double-walled plastic pots to help moderate temperature. The pots I got have a rounded, tapered inner wall with a single hole in the middle... I drilled four additional holes in the bottom to improve drainage. I've been pretty surprised with how long the pots are holding water - there is still water dripping out of the bottom 3 days after it rained, and it seems the soil is still pretty wet (based on my moisture tester) 6-8 inches down a week after watering. The citrus are in well draining citrus mix and the figs are in an organic potting mix. I have 1-2 inches of mulch on the top in an effort to minimize the soil from getting overheated by the California sun, but now I'm wondering if I need to get the soil to dry faster for the health of the trees. Is this typical for other with plastic containers - that they hold moisture for so long and water drips out of the bottom days after watering/rain? 

The trees themselves don't have droopy leaves or show obvious signs of overwatering, but they're not yet growing vigorously- so wondering if the soil is too wet.

thanks

Remove the mulch and replace it with a thin layer of light rock (lava rock, pumice) if you must have top dressing. Sun-driven evaporation works to your advantage if you're concerned about wet feet.

Does that mean you think it sounds odd that the soil is staying moist this long?

Yes, what you have described does not sound all that great for your plants.