If you take good care of it, a paint brush will last for years. Here's a few upkeep tips:
Seek out filaments that are sturdy yet flexible (nylon gives a smooth finish and is easy to clean); does the wooden handle have a good fit when you hold it? An all-purpose brush should be 2 or 2 ½ inches wide.
Try to keep the ferrule (that's the metal band that holds the filaments to the handle) as paint-free and dry as possible (dried paint and moisture can damage the bristles over time.
Limit your paintbrush dipping to less than 1 inch of paint; you'll have better overall control (and cleanup will be easier).
Wash away any latex paint under warm, running water (don't soak the brush). Using oil-based paint? Swish the brush in a cup of paint thinner.
Drag a paintbrush comb (available at paint and hardware stores) through the bristles to remove any remaining paint. Using the hole in the handle, hang the brush to dry.
Keep the cardboard cover your paintbrush came in; it's the best thing to maintain the brush's shape while stored.
Got any leftover paint? Can you donate it to a school, community group or use it on another wall?
If not, here's what to do:
Oil-base (alkyd) paint is considered hazardous waste; Never throw this away with the regular trash!
Check with your local waste management company to see if your area has a collection center or a designated day where you can donate the paint.
Water-base (latex) paint is not hazardous, so there's no need to take it to a special collection site (and besides, you may be charged. And who needs to pay extra money if you don't have to, right?). If you turn the paint into a solid, it can go into the regular trash (if there's a small amount left, leave the lid off to enable it to dry in a few days; mix in some kitty litter or sawdust in the paint; or get a solidifier, which hardens paint within a few minutes-go to www.cobzorb.com for an example). Get ride of the can and lid separately.
Source: “Brush Up”-Home Know-how segment-Better Homes and Gardens, Feb. 2011