The 12 year Time limit is required whether it is used part 91 or 135 isnt
it. the below add in trade a plane says not required for part 91 use.

1996 ROBINSON R44 ASTRO, s/n 0287, 1280-TT. Part 135 maintained, hangared,
AI, vert. compass, Mode C trans, 2nd FM Comm, Airwolf oil filter, primer. MR
blades due 2010, TR blades due 2016. Perfect ship for Part 91 operations.
Selling because do not want to perform 12 year inspection per RHC maint.
man. required for further Part 135 operations; however, new owner is not
required to perform 12 year RHC inspection if operating under Part 91.
Interior is a 8 of 10, exterior is a 8 out of 10. Clean ship with all
records. Never used for training! Priced for immediate sale! $135,000 USD.
Call Todd, MT/(406) 544-0402.