Be in pointe shoes as much as you can. Once you've gone beyond beginning pointe work, wearing the shoes for barre work is a good habit.
The sole of the foot, and ankle, have to work so much more with every tendu, degage, and rise onto demi-pointe. The shoe resists, and the muscles get a better workout.
If the thickness of the sole makes your foot wobble because it does lie flat on the floor, use a wood file, and shave the sole down lightly. You can get the sole close to flush with the satin, so that your foot will be flatter on the floor. Straining the ankles from wobbling is distracting.
Even wearing worn out pointe shoes is better than wearing soft shoes. There is still more effort needed, until the shoe is completely mushy.
There was a long thread on a ballet forum I was on recently, about keeping the shoes clean by wearing socks over them. You can do this safely by cutting a small hole at the heel, and one at the toe. The sock will go under the arch, but it won't be under part of the shoe that contacts the floor, causing you to slip.
And the socks will keep your ankles warm, too. Sometimes a ballet store will stock leg warmers that end in a sock-like part, with the heel and toe open.
Pointe shoes are beautiful when new, but get beaten up looking easily. When I was training, there was little concern about how long they would look new. Scuffs and worn satin were a sign of hard work.
If you have a performance coming up, it's different. Wear socks over them as needed. Try to have as many pairs as you need broken in to the same degree before your shows.
When your feet are totally sore and aching, use an ice pack! It is wonderful for pain and can be done several times an evening. (15 min. per hour max). But not touching bare skin.
Also, lying on the floor with your legs resting straight up the wall for a few minutes is good to help your muscles relax.
Work hard, and relax and stretch your muscles to keep the best tone.
Each ballerina in the English National Ballet gets an allowance of 10 pairs of pointe shoes ... every month. That means a pair of pointe shoes lasts just 3 days!