There is a new trend to start wearing heat molded insoles that you make yourself for a custom fit! However wearing DIY homemade insoles that you make yourself can be a bad idea (also stuffing your shoes with wool or other materials when they are cold can also be bad for your feet) even if it does save a little bit of money in the long run you can damage your feet and here are a few reasons why this is a bad idea.
If you decide to make your own insoles (even heat molded insoles) they will either give your feet too much support or inadequate support.
Using insoles that do not fit your feet properly which will usually be the case if you make your own can cause imbalances and alignment issues in your feet which can cause excessive strain and tightness in your ligaments which can result in injury. Not only that but it can put pressure on fragile ligaments in your foot and cause degeneration leading to osteoarthritis as the ligaments become more weakened and exposed.
Insoles like the ones you can buy here on In The Name Of Sport have been designed specially to absorb shocks and to target specific areas of the foot giving them just the right amount of support.
Custom insoles can be just as bad for your feet too because they can be too supportive and do not let your feet support themselves.