This can contains an oil-based painting primer, pigmented pure white, but it doesn't look that way. If you have a similar can of primer, think twice before throwing it out. Even though the contents look aged, it was sealed well, and with a little stirring, it will be perfectly useable for years to come.
In the case of many of your home products, project supplies and cleaning agents, looks can be deceiving, and you'll want to check the date, rather than the appearance of the product, to make sure you know how long a product truly lasts. Here are a few essential timelines and shelf lives to commit to memory or bookmark next time you open that can or bottle.
In order for any household product to last as long as possible, you need to know how long it was stored and how to store it. Water- and acrylic-based products, such as many cleansers and latex paint, should never be allowed to freeze, so your basement or utility room might be a better spot than the garage. Oil-based products won't freeze under weather conditions, and are best stored outside.
As with many things, the real enemy of long-term storage is air. So, keep your supplies in their original containers, and thoroughly clean the lids before storing to make the contents as air-tight as possible. If you plan to use the product over time (like a wood stain or an adhesive) instead of for a specific project (like painting a room), use a permanent marker to record the date purchased. Lastly, for complete storage info, simply check all that tiny print on the back label of the bottle or can and note what the manufacturer recommends.
These days, most home center and paint store products come in two varieties: latex and oil-based. Latex paints and primers are water-soluble and can last from three to five years, depending on how full the can is. Cans of latex paint that have never been opened will last from five to seven years, provided they haven't been frozen.
Oil-based paints and primers last much longer. If you can mix them to a uniform color and consistency, they can be used as long as 10-15 years after the purchase date. I like to use oil-based primer when painting MDF to prevent it from swelling. I've opened and reused the same can pictured above a few times a year for the last five, and after a stir, it works perfectly.
With any old paint, it's wise to test on a hidden area or scrap material to make sure it covers well and dries properly.
All-Purpose Spray Cleaners
All-purpose spray cleaners last at least two years in their original bottle. Check your bottles for specific expiration dates and shelf lives, or consider purchasing concentrates and mixing with water in your own spray bottle for longer lasting cleaning power.
Liquid Dish Soap
Dish soap will last from 18 months to two years. If you're looking for longer lasting soaps, consider unscented products, as it's the aroma additives that often break down the solutions.
Dishwasher detergents have the shortest life span of cleaners, lasting from six months to one year for liquids, and only a few months for powders or pre-packaged tabs. Contact with moisture will make them sticky, and the membranes won't dissolve. Of course, they shouldn't harm your dishes or pots and pans, but their efficacy will be significantly limited.
Liquid Laundry Detergents
Liquid detergents maintain their maximum cleaning power up to one year after purchasing. Be sure to cap them securely, and don't let any addition water get mixed inside. Remove any dried soap or residue from the mouth to prevent build-up and a less-than-stellar seal.
Powdered Laundry Detergents
Powdered detergents and stain-fighting additives will last for quite a long time as long as their kept dry.
Wood Stains and Finishes
With the exception of shellac, wood finishing products have a fairly long shelf life. Most can be stored for a minimum of three years, though many will last for several years after. The goal here is to stir thoroughly to redistribute any pigments, then test on a scrap piece. Also, be sure to test for any rust or other solid that may be in the stain, as they'll affect the finish and any additional coats. It's definitely not worth messing up a DIY or home improvement project you've invested hours or days into for a $10-15 can of stain.
Adhesives, Spackling Compounds and Fillers
These are likely the products with the shortest shelf life -- not because they expire, but simply because they're designed to spread and dry as they come in contact with air. With glues, contact cements, spackle, wood fillers and the like, you simply need to test them. If they'll spread evenly without lumps or chunks, they will work securely on your project. If not (you often won't even be able to clean the applicator or bottle cap), then it's time to replace. I use these products regularly, but buy the smallest tubes and bottles of specialty contact adhesives, wood fillers and wallboard compound for this very reason. Unless you're a professional, the larger sizes are not worth the money.