A frequent contributor is someone who regularly and consistently contributes or adds something to a particular group, organization, or project. Full definition
All those other names you mentioned are frequent contributors on here and we can only admire their generosity (time and experience). (biggerpockets.com)
Since 2013 she is frequent contributor for Artribune magazine and Digicult. (digicult.it)
Deming was a moderately - frequent contributor in 2004 - 2005, with a burst of 3 articles, of which the first two are discussed here. (rabett.blogspot.ru)