If the battery goes bad, you will lose all your info/settings.
A new battery will not restore any lost data. (Gone is gone)
Although the manual calls for replacement every 3-5 years; we find they normally last for about 8 years or sometimes more depending on conditions. If using the unit a lot, it will normally warn you about the battery being low. If you let the unit sit a lot without use, you might not ever see the warning because it doesn't have the opportunity to warn you.
Minimum you should keep some sort of backup of anything important to you (even if hand written). It could be a lightning strike tomorrow that take out the unit. Take photos of your waypoint list or something if you value the data. The dealer/service center can normally back up the points and change the battery. This way you typically don't lose anything if done before the battery goes bad.
