Should number of association employees be based on condo units?

I am the treasurer of a condominium association in downtown Chicago with 108 units and I am trying to get a better handle on our expenses and ROI. My question is this: (and I know that it will vary) is there a "general" rule that suggests how many full-time maintenance personnel should be "employed" by the condo association or management company given the number of units in a building?

For example, our building has 108 units; we have a full-time building engineer and a full-time janitor. I am not happy with their performance. On the other hand, the building across the street has 88 units, a full-time engineer and a part-time janitor once a week. Their building looks great. Any insight would be most appreciated. Thank you