A business will achieve higher cost efficiency with outsourcing the cleaning and maintenance work compared to having it done in-house. This is because in addition to the purchase of equipment and materials, the company will have to invest in the professional training of in-house staff. If additional workers are hired, the cost will climb further up. Given that the care for air vents and shafts is not a daily or even weekly task for the majority of businesses, it is simply not economical to go for the in-house option.
You should not wait as it usually means additional repair and in some unfortunate cases, loss of property due to fire. It is estimated that homeowners in US lose over $200 million due to use of unsafe systems.
You should also get the chimney or the venting system inspected whenever you make some change to your heating system or add an insert to the stove. This inspection will ensure that venting system, lining as well as chimney are working the way they should.