It is very important to wear them all the time except when in water eg Showers, swimming, and when asleep. The reason is the brain first needs to adjust to the way sounds are now heard because of the Aids and once adjusted to them it will affect you more when not wearing them than it used to. Some Hearing Aids can be waterproof and in those cases swimming and showering may be activities where you continue using them.
For some people full ear moulds are better than the thin tube ones that sit in the ear canal, some people can get away with using the complete in ear type of hearing aids. If you are an excessive ear sweater then make sure you use the hearing aid drying methods to ensure they are as free from moisture as possible each day, we find the replaceable desiccating discs in a sealed jar work well for us.
Have your ears checked regularly for wax build up and compaction as the wax 1) can reduce the sounds you hear, 2) it can block the hearing mould or tube rendering the aids useless until the wax is removed and 3) it can lead to a higher risk of or ear infections because of trapped moisture in the ear.
If you hearing aid supplier has a maintenance scheme it is worthwhile looking at paying for it. As we are pensioners we get Aids for free and the maintenance cost is about $45 a year for one of us (which allows us free batteries, cleaning, and repairs).
If you get another Hearing Aid set it is worthwhile seeing if your last old pair can be tuned to your current hearing needs and then keep them as emergency spares.
Check whether you can have the settings set for at least 2 types but preferably 3 types of use. These are normal usage, directional (they are set to pick up noise from in front of you) so in noisy environments you can concentrate on the person you are listening/speaking to in front of you, and loop setting also called T-switch which allows listening to sounds broadcast over a loop circuit or with telephones that allow this coupling. Some more expensive Aids can have other settings as well but these 3 are probably the major useful ones.
If your Aids support using a remote to adjust the settings it can make life easier than playing with the settings buttons on the Aids themselves but cost can be a factor.
If you are used to listening to music or want to hear when the doorbell or phone rings getting a loop system in your house can be a real benefit and if listening to the TV or music you can set it as high a volume as you need and not disturb anyone else.
Ahh @TheBBG beat me to my points but in regards to the coil many banks particularly their ATM machines now support coil/induction/T-switch Hearing Aids and it can make listening to the menus so much easier. Qld Rail at a lot of major and newer Stations support T switch and allow for much better hearing of train announcements (we use that a lot).