Most hearing-aid purchases go off without a hitch. But some don’t. It’s not easy to get it right because each patient’s hearing loss is unique and every patient has different expectations. Even two patients who have the same hearing loss on paper may have very different rehabilitative needs.

Also tricky: Since most hearing aids are custom-molded, patients can’t feel exactly how various makes and models would fit in their ears. But it is possible to try different technologies. Many BTE models can be fitted with special pliable earpieces and then set up for tests. The sound quality in the test should be fairly close to what you’ll get with your own customized device.

While such demonstrations can help you make your selection, no in-store test can duplicate your experience with a particular technology in real-life listening environments. Too much depends on your specific hearing loss, and a sample hearing aid will sound different from a custom-fitted one. For this reason, some audiologists prefer not to perform these demonstrations, and instead respond to the client’s real-life experiences by making adjustments as necessary. Ultimately, time and experience with a particular hearing aid are the only ways to determine how well it works for you.

There are laws to protect you from being locked into a hearing-aid purchase that does not meet your needs. According to District, Maryland, and Virginia law, you have 30 days after buying a hearing aid to return the aid for a refund. You may, however, still have to pay a portion of the hearing-aid costs. That portion varies tremendously from company to company: Some charge nothing; others charge a flat fee of $50 to $100; others charge a fee equal to 10 percent of the price of the hearing aid(s). So it is important to ask about refund policies and get a dispenser’s policy in writing.

Some dispensers offer trial periods more generous than 30 days. It is not unusual for a dispenser to allow 60 days or more for wearers who have special needs or who have bought particularly complicated hearing aids. If you feel you might need extra time to decide about an aid, ask the dispenser if an extension is possible and get the dispenser’s promise in writing.

Hearing-aid dispensers usually offer a free adjustment period during which they’ll provide assistance. This period varies, with some sellers offering free adjustments for six months and others for the life of the aid. If you are buying a hearing aid for the first time, or trying a new type of aid, find out about the dispenser’s policy regarding follow-up appointments.

Also, find out whether your return period will be extended if adjustments are necessary; if so, get this promise in writing. You don’t want to lose your right to return an aid simply because you’ve spent weeks or months trying to get it adjusted to meet your needs before concluding that it just doesn’t suit you.

To back up newly purchased aids, most manufacturers provide warranties of one or two years. In most instances, you can buy an extended warranty, as well.

You can also buy hearing-aid insurance to cover an aid for damage or loss, either as an add-on to a manufacturer’s warranty or as a separate policy. A hearing-aid dispenser should be able to provide information about insurance; also check with your homeowners insurance carrier, as you may be able to purchase a personal articles floater for hearing aids as part of your policy. Before buying any insurance, compare its premiums to the price of the aid. Usually, these types of insurance policies aren’t worth their premiums.

With luck, and some effort, you won’t need to buy new hearing aids that often. One way to expand your hearing aid’s lifespan is to keep it clean. The industry standard for a hearing aid’s lifespan is about four years, but it is not uncommon for hearing aids to last much longer—sometimes 10 years or more. On the other hand, hanging on to the same aid that long may deprive you of opportunities to take advantage of new technologies.