Bottom line:  Recommendations for tracheostomy management include daily cleaning of inner canula, as well as routine cleaning and daily inspections of the stoma.

Summary: 
Tracheostomy: Stoma Care.  Joanna Briggs Institute.  April 26, 2010.
Recommends routine cleaning and daily inspection for signs of infection in the skin around the stoma.  Evidence based on expert opinion.

AACN Procedure Manual, 6^th ed, 2011 .
Recommends monitoring skin around stoma for breakdown.

Tracheostomy:  Management.  Joanna Briggs Institute, October 29, 2010.  
Recommends cleaning inner cannula daily based on guidelines that did not cite studies, but relied on expert opinion.