Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
often [ˈɔfn] adv ча́сто
how often ...? как ча́сто ...?
more often than not ча́ще всего́
as often as not дово́льно ча́сто
every so often вре́мя от вре́мени
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: