Cheap insurance is to have the transmission back flushed by a mechanic with
the proper unit.  I have that done every other time I have the transmission
fluid replaced.  As I recall, you replace the filter, then back (or reverse)
flush the trans and fill to the proper level.  Normal drain and refill only
replaces about half the fluid or less.

Also, if it is an electronic controlled transmission you might want to run a
ground wire from clean shiny metal on the transmission to clean shiny metal
on the engine or chassis.  An aluminum transmission bolted to an iron block
with steel bolts can lead to electrolysis and even though it is a good
mechanical connection the electrical ground for the computer can become
degrade.  This is something the manufacturers are only now starting to
realize may be an issue and few mechanics understand.  A friend had gone
back to a transmission shop several times until I told him to try it - cost
him about $0.50 and the shop was charging him at least $100 for each visit.

I wouldn't rebuild unless you have serious problems.