I've been told that too-frequent cleaning will damage my things...

Well, not necessarily.  Here are some ways your possessions can be damaged by improper cleaning:

• Over-wetting - too much water left in the carpet or fabric
• Too high an alkalinity in the detergents used
• Too high a temperature for certain fibers
• Poor rinsing - detergent or other residue left in the fibers
• Use of cationic detergent where anionic is specified
• Use of overly aggressive dry solvents on solvent-sensitive material, or use of water on dry-clean-only material.

When the proper amount of the proper detergents and solvents are used at the correct temperature and all residues are removed, then cleaning is never detrimental. In fact, leaving your carpets or fabrics in a soiled condition is harmful to them.  Spots, spills, and stains become more difficult to remove the longer they're left alone.  Soil residue will "grind" away at soft fibers.  Oils will polymerize and bond to some fibers, causing permanent yellowing in some cases.