There are numerous ways to ensure a longer midsole life...not all including a repaint,
1, Purchase and insert a GEL insole (if enough room in your kicks,use with existing insole)
This acts to absorb more impact,rather than the midsole taking your complete weight.This really helps prevent cracking!!!
2. The process in which to repaint your midsoles can be as thorough as you want!!
You can simply strip all paint with acetone,and then repaint in Angelus Leather Acryllics...or an acryllic of your choice,and job done!!
But I chose a more robust approach.
This is my method for the AIR JORDAN III B.C for e.g,
I. Mask all areas around the white portion of midsole in FROG TAPE (for perfect,uncompromising lines)
II. Strip all white paint from midsole using acetone (applied with cotton balls/pads)
III, Clean midsole with warm soapy water and leave to dry (20mins min)
IV. Using the finest grade sand/glass paper, lightly sand the midsole in order to create a key the acryllic can better adhere to. you should not see any visible change in the surface integrity after sanding...this is a VERY LIGHT sanding only.
V. Remove all fine dust from midsole...you may not see any,but its there I assure you.I use a hairdryer.( may have to re-tape/mask now)
VI. Apply first coat of paint.
(Your weapon of choice depends soley on you.brushes can provide a great finish if applied in enough ultra thin coats..but ultimately an airbrush is less time consuming,and leaves a perfect 'factory finish'.)
VII. Each coat will need approx 20mins to cure at room temp...and amount of coats depends on if your using brushes or an airbrush.
( Brushes approx 4-6 coats, Airbrush 2-3)
VIII. Once happy with the consistency of coverage I strongly urge you to apply 2x coats of Angelus Acrylic Finisher. (This locks and seals the acrylic)
IX. Remove masking tape,and repeat process for the Black portion.
X. Enjoy your kicks!!!!!!!
The confidence in knowing that, whatever may happen I can still have my J's crisp, like straight out the box fresh...is priceless!!! its just going to take a morning of my time to bring them up...and I have like 20+ wears in all mines at least and they holding up neatly.But dont forget that gel insole too....it definately helps in taking majority of the impact away from the midsole.
Hope this helps,,,,,,Good luck