There are several questions to ask that will help you know that it's time to replace a piece of furniture:

Is the piece of furniture broken beyond repair?

Is the upholstery stained and threadbare?

Does the furniture still fit the space where it's used?

Is the furniture still comfortable to use?

Have your tastes and needs changed?

Sofa or Couch

If the sofa is creaking, the cushions are sagging, and all lumbar support is gone, it's time for a new sofa. Stained, smelly, peeling, or ripped upholstery are signs that a replacement or at least a new upholstery job is needed.

Upholstered Chair

The same replacement clues that apply to a sofa also apply to an upholstered chair. One additional thing to evaluate on recliners is the reclining mechanisms. If they no longer function smoothly, it's time for a new chair.

Wooden Chair

Whether a dining room chair or side chair, wooden chairs should be replaced if the legs have become wobbly or if the wood is splitting on the seat. If the seat is upholstered, the upholstery can often be replaced easily as long as the rest of the chair is sturdy.

Dining Room Table

Dining room tables may become unsightly from scratches, dents, and burns long before they become structurally unsound. Tables are usually replaced when a larger or smaller size is needed to comfortably fit a room and the usual number of diners.

Coffee Table, Side Table

Most coffee and side tables get lots of wear and tear from feet, hot coffee cups, and wet drinking glasses. They should be replaced when they become wobbly, look unsightly, or no longer fit the space and style of the room.

Bed

If a bed frame begins to creak, it's a good sign that you'll soon need to replace it. New bed frames can be purchased to attach to a favorite headboard, which usually lasts longer than the support system. Beds are often replaced as children grow from a toddler bed to a twin to a larger size.

Chest of Drawers or Dresser

Any type of drawer storage unit should be replaced when the frame is no longer sturdy and drawers no longer open and close easily. 

Desk

A desk should be replaced if it becomes wobbly or if any drawers do not open and close easily. Most desks are replaced as work and technology needs change.

Office Chair

If your office chair is used 40 hours per week, it will last around seven to 10 years. The lifespan will depend on whether the chair is made from solid wood, metal, or plastic and if it is leather or fabric covered. You'll know it's time for a new chair when upholstery becomes frayed and the chair becomes uncomfortable to sit in offering no lumbar support.

Patio Furniture

Whether made from rattan, plastic, or metal, patio furniture should be replaced when it becomes unstable and will not support the weight of an adult. You can extend the life of the furniture by keeping it out of direct sunlight, cleaning it routinely, and storing properly during the off-season.

Mattress

Your mattress is probably the most often used piece of furniture in your home. It should be replaced when it sags, has strong odors, and no longer provides the support needed for a restful night's sleep without back pain.