I recently completed a tour at a MH squadron and spent a total of about 20 months at sea. That works out to an average of slightly less than six months a year. However, in those four years I did two six month deployments and your last year on Sqn is usually in a HQ position where you tend to go to sea less, which tends to skew the average a bit. The specific Sqn manning at the time and the Navy's deployment schedule will affect how much any one person sails. However, I would venture to guess that you will spend between four - six months of your first three to four years on Sqn at sea (this doesn't include courses or other TD). I would suggest that if you think you will not like sailing on HMC ship then maybe the MH community isn't for you.
There have been a couple of past threads on what the TACCO job is like, however, your best source of info would be to ask any of the Nav instructors with a Sea King background at CFANS.
Fire away any more specific questions you have or PM if you prefer.
