There are several things that can shorten the life of a water softener. Homes with very hard water may have to replace the unit sooner because the water softener works harder to filter out the hard minerals. High water usage and infrequent maintenance can also put more strain on a water softener.

A water softener removes minerals from your drinking water and can make your house water softer. These softeners are designed to extend the lifetime of your plumbing system while also making water safer and more palatable for drinking. Hard water, which is water with a heavy amount of suspended particles, can also cause hair damage, skin irritation, and buildup in your pipes.

A tankless water heater should be at least 10 feet away from a water softener, although the pros you hire for water softener installation can help you determine the correct distance. These two units need to have some distance between them to prevent hot water from the tankless water heater from flowing backward into the water softener when it runs a regeneration cycle.

If your water softener repair is fairly straightforward, like a simple filter replacement, then you can probably do it yourself with little risk. However, anything beyond a simple fix should be addressed by someone with extensive plumbing expertise to avoid costly water softener problems, like leaks. 

That said, even simple problems can be complicated to diagnose, particularly if your water softener is attached to a whole-house treatment system. So, unless you feel absolutely certain that the problem is an easy fix that you can take on yourself, it's probably best to hire a plumber to diagnose and fix the problem.