This is the 9169th most frequent German word.
längerem
"Längerem" means "for a longer time" or "longer period" in English.
The word 'längerem' is used in the dative case, with 'seit' signaling a time span, meaning 'for quite some time'.
Ich habe seit längerem keinen Kontakt mehr zu ihm.
I haven't had contact with him for quite some time.
In this sentence, 'längerem' is in the dative case, used as an attributive adjective following 'nach' to indicate duration.
Nach längerem Warten kam die Nachricht endlich.
After waiting for quite a while, the message finally arrived.
Here, 'längerem' functions similarly, combined with 'seit' in a temporal context to mean 'for quite a while'.