Fetching details from the dictionary...

for a long time; at (great) length; lengthily; long-windedly; tediously
(extending) far; (stretching) out; (lying down) at full length
彼女は長長と手紙を書いて気持ちを伝えた。
She wrote at great length to convey her feelings.
ソファに長長と横たわって昼寝をした。
I stretched out on the sofa and took a nap.
長長とした説明を聞いて退屈してしまった。
I got bored listening to the long-winded explanation.